hybridfree/eevblog-posts huggingface dataset:
Made a few RGS-400 BNC Cables Today! - Page 1
Forum section: electronics / repair

author: Smoky
author_rank: Frequent Contributor
timestamp: October 05, 2020, 04:46:18 am
content: I needed a few BNC cables for my HP35660A DSA so I decided to make a few on my own. Pre-made ones are pricey so why not just buy the parts and the crimper since it adds up to about the same amount?The used Amp Pro-Crimper II came with the .068", .213", and the .255" die used to crimp the RG58 and RG59 varieties. I used Amphenol 000-36875 BNC's and the MilesTek 10-21001-240 crimp-on RCA plugs. The die size used for the BNC's is the .213" and the RCA plugs required the .255". The .068" die wasn't used since I soldered the center pins. The RGS-400 coax is made by Thermax.All I can say is SweeeeetI made two 36" BNC to RCA cables, one 36" BNC to BNC, and one 12" BNC to BNC. The 12" cable will be used to send the "Source" signal of the DSA directly into its Channel 1.Spring clamps securing the cable while working on it was like having a second set of hands. I trimmed the RGS-400 cable by hand too and used Kester's silver solder for the soldering of the pins. I tested all cables with the DMM for shorts afterwards.I plan to make more cables in the future but I'm going to give the RG-316D double-braid a try. I imagine it will be more flexible than the RGS-400 but still shield audio frequencies just fine. It'll require a .176" crimp and I see a replaceable die for the Amp Crimper for sale on Ebay too!
Magic Smoke form Dyson Fan  AM07 - Page 1
Forum section: electronics / repair

author: calli
author_rank: Regular Contributor
timestamp: May 24, 2019, 04:05:59 pm
content: Just got a Dyson Fan for checkup.That must have released some magic smokeI suspect a water damage, some rust on the bottom plate and the marks look like corrosion, the capacitor seems ok, so the white stuff is not from it.Chip blown and a hole in the pcb....RIP.
Magna-Mike 8500 - repair of keypad - Page 1
Forum section: electronics / repair

author: mendip_discovery
author_rank: Super Contributor
timestamp: December 07, 2021, 07:48:23 pm
content: So I have been asked to see if I can get the keypads on one of these repaired (example pic attached). The measure and calibration and on/off buttons have all been used so often that they are no longer working. Of course, the unit has been discontinued and spare parts aren't available.Is there an affordable way to repair the keypads, doesn't have to be like new, but given the replacement, units are 10k it's worth a punt to see if they can be repaired.Also looking to make a new power supply, but getting a little confused on the Lemo connectors, its a FFA.OS with 2 pins but what is the difference with the 303/304 etc. ? Pics of the connector are attached.
magnavox cm8702 074g power button repair - Page 1
Forum section: electronics / repair

author: Burnrate
author_rank: Newbie
timestamp: April 09, 2022, 06:04:07 pm
content: Good morning. I have a Magnavox color display 40 (magnavox cm8702 074g) and it will turn on but turn off when I release the power button. Sometimes I can jiggle it to get it to stay on but usually it will turn right off if I release the button.It is my understanding that it most likely has a switch like thisand that the little slot at the top may be filled with some dried grease or something. I could try to spray some lubricant in there but don't really want to without knowing what is behind it.Any tips or repair info or guides to taking it apart?

author: CaptDon
author_rank: Super Contributor
timestamp: April 09, 2022, 06:41:57 pm
content: That is a very well known issue with the North American Philips product line (MaggotBox, Sylvania, Philco, etc.) That switch is available as a replacement part and is common. You need to find a local T.V. repair shop or look it up online. I have an identical monitor and I just left mine broken. I had one of those older units for use with a computer that had all the power switches on the front panel for Computer, Monitor, Printer, etc. I have personally replaced at least a dozen of those switches during the years my father operated a T.V. repair shop. I think MCM electronics and other aftermarket providers still list that switch!

author: Burnrate
author_rank: Newbie
timestamp: April 09, 2022, 08:12:42 pm
content: How do you remove the switch? Do you just pull it out and it pops out? I don't want to snap something but if I can get it apart I'm sure I can take care of it.

author: Burnrate
author_rank: Newbie
timestamp: April 09, 2022, 09:56:43 pm
content: So the thing in the middle of this picture is the bad switch. It has the power cable coming in attached to it behind it in the picture. You can see the cable going to the power button light on the left of it. The power button doesn't even actually attach to the switch, it just pushes against a plastic pillar that is part of the switch.I would really have to take the whole thing apart to get to it properly. I'll try to get it stuck in the On position again and if I do that I'll unplug it to turn it off and keep an eye out for a place that would do a good job of fixing it.

author: Burnrate
author_rank: Newbie
timestamp: April 09, 2022, 10:04:40 pm
content: I am wrong, the boards on the bottom slide right out! So easyI can just unscrew the switch and get a new one somewhere. I'll have to resolder the power cables back on but it's all so easy to access.

author: Burnrate
author_rank: Newbie
timestamp: April 10, 2022, 01:08:08 am
content: Since I am lazy and like instant gratification I simply removed the spring from the switch and it now sits in the on position.
Magnetek HPV900 Series 2 variable frequency lift drive PSU problem - Page 1
Forum section: electronics / repair

author: rectifier
author_rank: Newbie
timestamp: April 21, 2025, 07:55:15 am
content: Hi,I have a Magnetek HPV900 Series 2 variable frequency lift drive with a fault in its SMPS.This should create +5V, +/-15V DC and +24V DC. Actual measured values by me are +4V4, +/-16V8 and +29V8 DC.The LCD display on the controller shows 'CF00 OP Comm. Err1', and no red LED, and does not respond to any button presses. I have replaced three electrolytics on the secondary side of the SMPS, which measured out of spec. (low uF values, high ESR) but the problem persists.I'm currently reverse-engineering the SMPS to try and fix the fault because Columbus McKinnon won't give me the schematic to speed up the detective work. I emailed them directly last week and they politely refused. My customer rang them a while back, described the DC measurements and error code and their technician said 'it's the power supply' (which is at fault).The attached photos might be useful, but notethe customerhas written dashes next to T11 and T12 which could be misinterpreted as minus signs. The values I measure are positive, so he's just wrong there.Anyone here able to assist please?

author: MathWizard
author_rank: Super Contributor
timestamp: April 21, 2025, 10:34:25 pm
content: Strange that the rails are that much higher, or is that just without a load on it ? What do the rails look like on a scope?I'm guessing the 4.4V is running the LCD, that sounds pretty low too. A typical 5V regulator should be within +/-0.1V. Now a lot of SMPS's will have a mini SMPS making just 5V STBY or similar low voltages on the primary and maybe the secondary side too, like for the LCD. And 4.4V sounds like an odd number for 1 of them, I'd be looking at the controller IC for that too. Maybe it's all the same controller tho.IDK what kind of SMPS they use to run motors. But the problem could be something as simple as a voltage divider, having resistors drift, or caps start leaking, and then some IC could be sensing the wrong voltage, and then letting those rails get too high.
Magnetron Switching power unit - Page 1
Forum section: electronics / repair

author: hitecelec
author_rank: Regular Contributor
timestamp: June 09, 2021, 11:02:04 am
content: HiI am looking for a SVC manual of Alter PM 250 Switching unit for MagnetronPicture attachedThanks in advance

author: coppercone2
author_rank: Super Contributor
timestamp: June 10, 2021, 03:10:03 am
content: is this a wood dryer?
Main Firmware checksum error on HP esa-L1500a - Page 1
Forum section: electronics / repair

author: dandan
author_rank: Newbie
timestamp: November 07, 2022, 11:32:31 pm
content: I have a problem with a HP ESA-L1500A spectrum analyzer. When it is powered up the screen appears very bright but nothing is displayed. I have checked the voltages on the motherboard and all seem ok. The eight status leds on the processor board stops almost immediately after power-up giving 11111010 (Main Firmware Checksum) error. Does this mean the firmware needs to be reloaded, and if so, how do you perform this on an analyzer that does not have a disk drive and a display thats not working?
mainboard intel dh87mc no video - Page 1
Forum section: electronics / repair

author: nato
author_rank: Newbie
timestamp: June 20, 2025, 12:34:13 am
content: Hi everyone,I'm currently diagnosing an Intel DH87MC motherboard that uses a Nuvoton NCT6683D-T Super I/O chip.Symptoms:- Board turns on when Power button is pressed.- Super I/O firmware (MX25L400) is read — CS# activity is seen on oscilloscope.- However, CS# enters an infinite read loop.- No POST, no video, no beep, no LPC POST code.- BIOS chip (W25Q64) is properly flashed (8MB, full image with FD + ME + UEFI).- 3.3VSB, 5VSB and 1.8V internal regulator (PAD_CAP) are all OK.- RTC crystal (32.768 kHz) is oscillating.- Main crystal (14.318 MHz) only oscillates in S0 (expected behavior).- BIOS Recovery via USB .BIO file does not trigger any activity.Based on all this, the EC seems partially alive (power on works, SPI is read) but does not execute its firmware correctly or fails to signal the PCH to begin POST.What I’m looking for:- Pinout or schematic info for the NCT6683D-T- Boardview or schematic for Intel DH87MC- Any known Intel boards that also use NCT6683D-T- Confirmation of key signals: RSMRST#, PLTRST#, XIN/XOUT, etc.Any help is welcome. I’ve documented the full repair process and would be happy to share.Thanks!

author: GGMM
author_rank: Frequent Contributor
timestamp: June 20, 2025, 08:02:21 am
content: re,I had a similar problem on an old motherboard. it came from the bios that I had to reflash.I skimmed the documentation, I think there is a backup of the bios.Before manipulating see if access bios and settings, try with a video card, etc...cdt

author: GGMM
author_rank: Frequent Contributor
timestamp: June 20, 2025, 08:06:44 am
content: some ideas for the bioshttps://community.intel.com/t5/Intel-Xeon-Processor-and-Server/DH87MC-BIOS-Update/m-p/1549455good luck

author: nato
author_rank: Newbie
timestamp: June 22, 2025, 01:46:14 am
content: Hi GGM, I'm telling you, I've already tried with another BIOS, I even managed to dump both the BIOS and the EC and it's still the same, the cs# pin (the loop is on the EC flash), rsmrst# is not released (the strange thing is that the board does manage to turn on but there is no activity on the LPC bus) I think it's the SIO, I've already ordered one, when it arrives I'll try it and tell you how it goes.
Making adapters for HP 1630 series logic analysers. - Page 1
Forum section: electronics / repair

author: CDI1977
author_rank: Contributor
timestamp: June 12, 2019, 08:04:50 am
content: Anyone still looking to make their own adapters, I just got around to it.After long hours of looking I found these are connectors are still available.TE Connectivity 280595 receptacle housing 12 position.TE Connectivity 182198-1 Tin contact, crimp. (Gold flash also available.)Crimping tool, I used the PA-09Cut down housing to 11 positions, file off protrusions except for wire entry side.Apologies, the solution to the high force may be obvious to some but to avoid possible damage the connector needs to be filed down.I do have one original HP adapter and I measured it as 5.85mm. I measured the replacement connector as 6.25mm. Anyway filing both sides down to less than 6mm fixes the high force. The polycarbonate is easy to work with a rough file.Please note, it takes some force to seat the connector and to remove it. My concern is the ceramic PCB but so far so good.
Making USB sticks work with Rigol stuff - Page 1
Forum section: electronics / repair

author: ramenbytes
author_rank: Contributor
timestamp: July 14, 2025, 11:38:40 pm
content: Hello!I recently had a problem trying to get data off a Rigol RSA3015N, which is one of their real-time spectrum analyzers. I'd plug in my USB stick (a 16GB SanDisk Cruzer Edge from 2016/17 or before), it'd note that I plugged a drive in, but when I flipped to the file browser there would be no external storage available. I did some searches online, and people seem to have had similar problems with Rigol scopes.After some kagi searching, I found this article:https://chris.harrington.mn/techsupport/2022/04/16/rigol-ds1202z-e-usb-error.htmlAccording to the author, they've determined (but not explained how or why) that some Rigol scopesdon'tlike USB drives with a GPT (GUID partition table). Well, my drive was labeled DOS, so that wasn't it.However, I had been running it without any partitions. No problems on Linux or Windows so far beside feeling funny about not having any numbers at the end of "/dev/sdb". But after reading the article I suspected that the Rigol might not be smart enough to deal with that. I popped the drive into my computer, re-created a MBR (DOS) partition table for good measure, made one big partition for the whole USB drive, formatted it to FAT32, and popped it into the SA. Et voila! It works!I did a quick search on the forums for "rigol gpt" to see if anyone else had discussed the article or it's findings, but didn't see anything. So I made this quick post both to call attention to the article and to let others know what worked for me. Hope it's useful to someone!
Makita bmr100 - Page 1
Forum section: electronics / repair

author: christensen
author_rank: Newbie
timestamp: July 24, 2023, 12:27:25 pm
content: Hi,I got a Makita bmr100 with error displaying and no power up. just 'E' and discharged battery simbol.It is happening after using a while (30 min) and than constantly. If i stop it will not turn on, or if i leave on after a while will stop it and will display the error.When i remove the power and reaply it will work a few minutes(depend how long was working).On the board cannot find anything overheating. The test i've run with/without auxiliary battery and doesn't made any difference.I've separated the boards and tested independently, the issue is from controller board (display).During testing i've noticed that when DC-Ref pin 44 of TC9318AFAG controller will drop. don't know if it's the cause or effect.
Manhattan HDR Freesat Tuner - Degraded Output - Page 1
Forum section: electronics / repair

author: xyberlink
author_rank: Contributor
timestamp: February 23, 2025, 02:33:49 pm
content: Hi,I have a pair of Manhattan Plasa HDR.S Freesat Receivers.Unit 1 doesn't boot (ignore that issue for now).Unit 2 boots and appears to work normally* but there's an issue with the picture / sound.* I say normally - there's an issue with the hard drive not being recognised (ignore that for now).So.... Unit 2....- Is connected to a known good Sat feed (works fine with other Sky / Freesat boxes).- Signal quality is 100% with a strength of ~80%.- It finds and tunes in 130+ channels.- When I try to view any channel, I get a odd snippets of sound / picture - I'd say it's about 5% working.If I borrow the sat input board from Unit 1, Unit 2 then works about 80% - some channels are just about ok, others are ok ish with some artifacting / picture breakup.Given that swapping tuner module changes the symptoms significantly, I'm thinking the issue sits on the tuner module rather than the mainboard. I get the feeling the tuner boards are degrading. The board in Unit 1 is almost totally gone, while Unit 2's board has started to degrade.The question is..... does anyone know what might cause these to degrade and is there any fix?The obvious candidate to me is the capacitors - but they appear to be fine. They look fine. I've also removed a few and they test spot on (both for uF and ESR). Caps on the mainboard also appear to be in good order. I'm not sure what else to try.Any guidance / thoughts greatly appreciated.Thanks,Paul.
Manson HCS-3602 Power Supply lost its values. (HCS-3600 series) - Page 1
Forum section: electronics / repair

author: Wollvieh
author_rank: Contributor
timestamp: December 08, 2024, 12:01:59 am
content: I saved a Manson HCS-3602 from the dumpster. Labelled as Peaktech P1580, but that doesn't change much.Manson Manual attached.Technically it's in perfect condition, but it does have a software problem. Most likely the stored values are lost.When powered on, it goes successfully through all tests.It starts with 0 V, 0 A on the display. Then it says "UuL" or "UcL" when trying to select a voltage or current above 0. According to the Manson manual this means those limits have been set by software and can only be removed the same way.The provided software doesn't connect. But I managed to connect via hterm and send commands, where the Power Supply answers.The answer to "GMAX" is "000000", which is bad. Because these are the maximum values of voltage and current the Power supply can deliver. I assume originally this was factory set to the specific type of supply. So this brick now thinks it is a 0 V, 0 A supply. Any command to change voltage or current is only accepted when the value is 000.The controller I see on the digital board is an Atmega 64A. No other digital chips, especially no EEPROMS.So no way to set the values or to read them from a different device? Or was Manson so kind to not set the lock bits?

author: Wollvieh
author_rank: Contributor
timestamp: December 16, 2024, 11:13:30 pm
content: Has anyone ever tried to read out the EEPROM of the Atmega 64a in this power supply?One might assume that all the fuses are set correctly (=putting the µC in an unserviceable state), but you never know.I have no experience in programming Atmegas, so I'm not sure if I understand the datasheet (which I attached here) correctly:Table 31-2 on p. 383 says there is a memory lock mode for "further programming of the flash and EEPROM" and another one for "further programmingand verificationof the flash and EEPROM".Is the second one the usual one to protect the program? So if the program is protected, the EEPROM is also unreadable? Or is there a fair chance to be able to read the EEPROM and its configuration data?
Manson NP_9615 linear power supply - Page 1
Forum section: electronics / repair

author: gencomm
author_rank: Newbie
timestamp: September 22, 2019, 09:14:20 am
content: I am seeking a schematic for a Manson NP_9615 linear power supply .Can you help me?

author: JFJ
author_rank: Regular Contributor
timestamp: September 22, 2019, 12:10:50 pm
content: If a schematic for your power supply is unavailable, then the attached schematic (for a similar model) might help.

author: gencomm
author_rank: Newbie
timestamp: September 26, 2019, 06:33:23 am
content: Thank you JFJ,It is the same board.Would it be too much to ask for a silkscreen view of the PCB (4510-9600-0002)?Anything I can do for you in the field of radio comms ?

author: JFJ
author_rank: Regular Contributor
timestamp: September 26, 2019, 05:43:52 pm
content: Quote from: gencomm on September 26, 2019, 06:33:23 amSorry, the schematic is all that I have.A few years ago, I obtained a service manual for a Tenma 72-8340A switch-mode power supply. The manual turned out to be a Manson document that covered their NPR-2050, 3630 and 6016 power supplies. If you can identify a re-branded version of your power supply, then a service manual might be available from a supplier of an alternative brand.

author: paul8f
author_rank: Regular Contributor
timestamp: September 27, 2019, 06:54:00 am
content: Quote from: JFJ on September 26, 2019, 05:43:52 pmWas it a pure coincidence, or is there some way to find out what other brand-names a product gets marketed under?Service Manuals like this are an invaluable tool in the push for the 'Right to Repair', and e-waste management/recycling.

author: gencomm
author_rank: Newbie
timestamp: October 06, 2019, 04:59:45 am
content: I have looked for alternatives with nothing extra found.I have got it operating but with a few inconsistencies still.I have a little trouble getting my head around the cct fully.Many thanks for your help.regards,John.
Manson NRP-3630 power supply current feedback stability issue - Page 1
Forum section: electronics / repair

author: bborisov567
author_rank: Regular Contributor
timestamp: April 11, 2025, 08:24:19 pm
content: The initial problem of this supply was that with the output shorted Q7 and Q8 would blow along with the fuse. Initially i thought the problem was in the transistors but then it happend again so i decided to measure the response of the current and voltage feedbacks. I use 15 ohm injection resistor marked Ri for the current and Rv respectively in the schematic.Regarding the voltage feedback - it starts from 0 dB which is a bit unusual.Regarding the current feedback - with C41 being 22 nF (on the schematic it is 100 nF, but 22 nF cap was populated) it looks stable but the crossover freqeuncy is around 30 Hz. I suspect that might be causing too much current for too long to flow through Q7 and Q8. I replaced C41 to 6.8 nF which shifted the crossover to 100 Hz but now there is a spike around 2.5 kHz going above 0 dB. I tried adding 68 pF in paralel with C41 and R41 in order to make a type 3 compensation but that didn't change anything.Still i haven't done any calculations but that might be the next step. TL494, both op-amps and the driving transistors have been replaced. What are your thoughts about this case? Could a slow feedback really cause the transistors to blow?Full schematic is available herehttps://media.elv.com/file/71970_nrp3630_data.pdf.

author: Harry_22
author_rank: Frequent Contributor
timestamp: April 12, 2025, 10:12:07 am
content: Hi!What about the other components at gate Q8 (Q7)? Have you checked R33, Q6, ZD3, R32, D7 and so on?Most probably some of them have to be replaced if the gate of MOSFET shorted.

author: bborisov567
author_rank: Regular Contributor
timestamp: April 14, 2025, 08:24:30 am
content: Quote from: Harry_22 on April 12, 2025, 10:12:07 amYes. i have replace all the components regarding the driving circuitry of the mosfets. Both mosfets have nice and clean gate impulses now.
Manual for Keithley 225 Missing Crucial Pages - Page 1
Forum section: electronics / repair

author: bap8guy
author_rank: Newbie
timestamp: April 29, 2020, 02:33:47 am
content: I need to calibrate a Keithley 225, but the manuals I have found all are missing pages 13 and 14, which are crucial to the calibration. Does anyone have them that could share, or point me in a direction to find them? Thanks.

author: Dr. Frank
author_rank: Super Contributor
timestamp: April 29, 2020, 07:37:12 am
content: This manual seems to be complete, though the page numbering is different:http://web.mit.edu/8.13/8.13d/manuals/keithly-225-current-source.pdf

author: bap8guy
author_rank: Newbie
timestamp: April 30, 2020, 07:42:43 pm
content: I did find the missing pages, but they were tucked in with the schematics at the very end of the manual. Thank you.
Manual/schematic for HP 6186C - Page 1
Forum section: electronics / repair

author: xantia_99
author_rank: Contributor
timestamp: May 16, 2019, 01:35:39 pm
content: HiNow I search for a manual with schematics for the HP 6186c current source 0-100 mA and 0-300 Volt. Most of the current part works but the voltage limit function have severe problem.The transistors looks OK after some changesAs I have seen here before it exist quite a good manual but without schematic and one version with a very bad schematic.I look forward to hear if someone have any news in this area.Best regardsStephan

author: duak
author_rank: Super Contributor
timestamp: May 16, 2019, 05:03:57 pm
content: Here is a scan of a manual with schematic:https://neurophysics.ucsd.edu/Manuals/Hewlett%20Packard/Current%20Source%20Model%206186c.pdf

author: Ordinaryman1971
author_rank: Frequent Contributor
timestamp: May 17, 2019, 06:01:59 pm
content: I've had a problem on mine when the compliance voltage was stuck at about 60V with just a little wiggle but no way to adjust it.I've traced the problem to one of the TO-3 transistors.... 2SC1576, they are hand picked for this application and very hard to find.I'm still waiting for replacement so the current source is just sitting on the side of my desk....Just wanted to add, it's beautiful design and show me another one with 300V compliance voltage that would be that affordable.

author: xantia_99
author_rank: Contributor
timestamp: May 17, 2019, 07:48:43 pm
content: I had to change two 40327 voltage limit current source breakdown and now the current looks okay. But my new yellow light diode in the old limit light turns off at 100 volt. never get higher than that. Looking at around at all zenerdiodes and stabistors just now.But the schematics make me crazy.RegardsStephan

author: xantia_99
author_rank: Contributor
timestamp: May 23, 2019, 08:06:22 pm
content: HiAfter some work I found several zener diodes out of order, shortcut, lost value. So in the end I found the lost 230 volt. Now it's up and running again, some small adjustment left, as calibrate and clean up all the temporary solutions.Best RegardsStephan
Maplin 50 watt amp fix - Page 1
Forum section: electronics / repair

author: nigelwright7557
author_rank: Frequent Contributor
timestamp: January 09, 2020, 08:44:18 am
content: Recently bought in a Maplin 50 watt hi fi amplifier off ebay that wasn't working.I replaced the missing obsolete parts with bits off ebay.The amp sort of worked but was heavily distorted.I checked all component for value and they all seemed fine.The voltages didn't seem quite right around one of the transistors.So I checked the transistors again using diode check and all tested ok.It then suddenly hit me the transistor with the wrong voltages tested ok but was PNP instead of NPN !It looks like a previous attempt to fix it went wrong.I managed to get a new transistor off ebay and the amp now works fine.Amps can be hard enough to fix but having wrong components fitted really makes things hard.

author: Gyro
author_rank: Super Contributor
timestamp: January 09, 2020, 10:54:57 am
content: I remember that the 50W amp kit was documented in one of the Maplin magazines (as were all of their kits). I can't remember which issue, but you can find them all here...https://www.americanradiohistory.com/Maplin-Electronics.htmMy guess is '80s.Good hunting!EDIT: Ahah, July 1993.

author: mikerj
author_rank: Super Contributor
timestamp: January 09, 2020, 12:13:23 pm
content: I remember the 50W Maplin amp very well, it was a pretty nice sounding amp but a flaw in the original design was the use of nylon nuts and bolts to mount the output transistors rather than using top hat insulators with steel fasteners. The nylon fasteners would fail, shortly followed by the output devices so if yours is still using the plastic parts get them changed out ASAP.

author: floobydust
author_rank: Super Contributor
timestamp: January 10, 2020, 02:59:23 am
content: pics and schematic of the 50W Maplin amp. Nobody knows if it's a John Lindsey Hood design. He did the 75W version after.I am familiar with the 75W MOSFET and 225W Disco kits.

author: nigelwright7557
author_rank: Frequent Contributor
timestamp: January 11, 2020, 05:16:18 am
content: Quote from: floobydust on January 10, 2020, 02:59:23 amI have a few of each of those amps.
MARANTZ CD44 User and/or service manual - Page 1
Forum section: electronics / repair

author: rkabz
author_rank: Contributor
timestamp: May 28, 2022, 02:32:17 am
content: Hi group, looking for any info for a Marantz CD44 CD player. Already discovered it's a re-badged Philips CD-104 and have all relevant CD104 stuff, but would like original info if anyone has pdf scans, or if you have a paper copy you don't need. I've repaired it using the Philips info. Recapped, re-soldered 'griplets' and dry joints and now working beautifully. Thanks.
Marantz SR 320 Service Manual - Page 1
Forum section: electronics / repair

author: Oldman79
author_rank: Contributor
timestamp: February 23, 2022, 08:23:45 am
content: Hello Helpful folksI am looking for a pdf copy of the service manual for a Marantz SR 320, any one known of a free resource to look for a copy?

author: PKTKS
author_rank: Super Contributor
timestamp: February 23, 2022, 12:01:33 pm
content: https://www.hifiengine.com/database/hifi_database.php
Marantz SR-4002 AV receiver Sound Problem (?) - Page 1
Forum section: electronics / repair

author: Comp_Sci_hater
author_rank: Contributor
timestamp: September 22, 2024, 10:04:34 pm
content: Hi everyoneI just got my hands on aMarantz SR-4002AV receiver, it stood in my living room for the past 12 years. The complaint from my parents is that the sound is very quiet even on the highest possible volume, furthermore the receiver wasnt redirecting the hdmi input from our PS4 to the TV. The other thing that i am not sure is an issue with the receiver or with me, is that i couldnt get all the channels to work (surround left, front left, center, front right, surround right). I connected the audio to the AUX port on the front and the only channels playing sound were Front left and right, i couldnt figure out how to make all of them work for 4 hours. After that i noticed the surround channels and the front channel were outputing sound, the sound was just so quiet that even with my ear on the speaker i could barely hear them.Does anybody own this receiver or even the newer/older version and could give me some tips how to set this thing up to work on all channels? The quiet sound is probably something messed up in the circuit, same with the HDMI, but the problem with only front channels playing reasonable sound is strange, because even in the multi channel stereo preset they were quiet.Thanks in advance for all the responses.
Marantz SR-940, Tape ON/OFF not working, help please! - Page 1
Forum section: electronics / repair

author: SAS73
author_rank: Contributor
timestamp: September 30, 2023, 06:19:32 pm
content: Hello friends ,Trying to troubleshoot Marantz SR940 receiver.Tape ON/OFF function is not working.Can somebody explain how this schematic works ?What I understand is when Tape ON/OFF switch is pressed I should have 14 volts go to D515 and D516, and then transistors Q517 and Q516should send 14 volts to electronics function switch TC9151 pins 19 or 20.Pin 19 tape is ON, Pin 20 Tape is OFF.This not happening no flipping voltages from Q517 or Q516, checked transistors and diodes , they are ok.Any Ideas ?Help please !

author: David_AVD
author_rank: Super Contributor
timestamp: September 30, 2023, 10:41:13 pm
content: Have you checked that the switch itself works?Do you have a link to a pdf copy of the service manual? Too hard to trace with the fragments posted.

author: SAS73
author_rank: Contributor
timestamp: September 30, 2023, 10:51:43 pm
content: Thanks David ,Yes I checked, switch itself is working correctly.Here is a link for the service manualhttps://easyupload.io/d4c75c

author: David_AVD
author_rank: Super Contributor
timestamp: October 01, 2023, 04:56:57 am
content: This is typical of Marantz making circuits much more complicated than they need be.It looks like the button goes through C510 which would make the press into a pulse, not a steady state.I haven't looked much beyond that, but I'm sure I've had to replace a TC9151 before due to it doing weird things on some input selects.

author: SAS73
author_rank: Contributor
timestamp: October 01, 2023, 02:28:10 pm
content: Thanks David!Replaced TC9151P, same issue, injected 12 volts from external P/S to pin 19 , it`s mutes FM radio and Tape source is playing (so it`working from external P/S)The best I can understand it`s when I press TAPE btn it`s charging C510 to 14 volts, but then I am lost , I don't understand how Q516 , Q515 is switching ?The switching signal goes to emitter ?This is bugging me !Help please!P.S. IS THIS A FLIP FLOP circuit ?

author: SAS73
author_rank: Contributor
timestamp: October 02, 2023, 12:01:16 am
content: UPDATEAfter hours of troubleshooting, gave up, assembled the flip flop circuit (couple of transistors and miniature relay)Bypassed the original TAPE select circuitry, and it's working now!Still don't understand, what is "wrong" with the original circuit.

author: David_AVD
author_rank: Super Contributor
timestamp: October 02, 2023, 12:22:09 am
content: Like I said, Marantz often have some weird arse circuitry that's sometimes hard to decipher. lolIt is probably some sort of flip flop, with with way more components than anyone else would use.

author: SAS73
author_rank: Contributor
timestamp: October 02, 2023, 12:24:32 am
content: Yep. You are right about Marantz, but it`s sounds amazing !
Marantz SR7005 AC Receiver Pop on 2nd Startup Relay - Page 1
Forum section: electronics / repair

author: bighalf
author_rank: Newbie
timestamp: January 17, 2023, 06:30:37 am
content: Hi guys, I have the subject receiver and it has developed a loudish momentary pop when starting up. The process seems the receiver turns on, prepares itself for a few seconds, and then a relay clicks and sound starts. Most of the time it’s fine, but occasionally on that second (delayed) relay click, there’s a pop.I wonder if anyone has had a similar experience, and identified what was the cause? It’s a 10 year old unit, but I can’t see any obvious caps bulging etc, and don’t want to replace stuff unnecessarily!

author: Martin72
author_rank: Super Contributor
timestamp: January 18, 2023, 10:53:42 pm
content: Hi,Normally the delay after power on and switching the output should prevent a popping sound(Time to stabilize the circuits).I would check the speaker outputs for a DC offset voltage, measuring with a multimeter.Then checking the railvoltages for being appx similar, e.g. +/-50V.If there´s a remarkable difference between + and - rails, check the electrolytic caps, they could be weak without any optical signs.(Further things:- Is the popping sound on every output ? That would speak for the "Electrolytic cap damage theory", when all channels are affected.- Unbalanced rail voltages causes the offset on the output, when the offset voltage is gone after popping it´s another point which speaks for a damaged/weak cap(s).)
Marantz UD7007 universal player - Can't find jumper/solder bridge on new laser - Page 1
Forum section: electronics / repair

author: Bargainhunter
author_rank: Regular Contributor
timestamp: February 27, 2023, 10:20:06 pm
content: I am replacing the laser pickup on my Marantz UD7007. On other pickups I replaced, there was a solder bridge to protect the laser that had to be removed.On the new pickup and on the bad pickup that came in the Marantz, I can not find any jumper or solder bridge. Has anyone ever replaced a laser pickup that did not have a jumper or solder bridge? I have attached two photos of the new laser pickup. Maybe I am overlooking something.Thank you.
Marconi 2019 - Reverse power protection - Page 1
Forum section: electronics / repair

author: Erik L
author_rank: Contributor
timestamp: December 10, 2023, 03:09:19 pm
content: Hi there,Some time ago, my Marconi 2019 became locked in what I believe is a reverse power protection mode. The keypad is frozen, unresponsive, and the LED labeled "RF LEVEL / REV PWR RESET" is lit (please refer to the attached picture).Does anyone on the forum have any insights or experience with this issue?Any help would be greatly appreciated!Erik

author: George Edmonds
author_rank: Frequent Contributor
timestamp: December 10, 2023, 05:38:10 pm
content: Hi ErikPlease post your question at Marconi-Test-Instruments@groups.ioPlenty of help available thereG Edmonds

author: Erik L
author_rank: Contributor
timestamp: December 11, 2023, 01:47:55 pm
content: Thanks George!I post it in a new topic on Marconi-Test-Instruments@groups.io, not sure about how to attach the picture tow.Erik
MARCONI 2022D RF GENERATOR - Page 1
Forum section: electronics / repair

author: RADIOAMAT
author_rank: Newbie
timestamp: July 23, 2019, 09:37:34 am
content: HiI have my RF generator MARCONI 2022D andit remains blocked on the start-up phase with the display 2022This is the version with EPROM 27C512 soft 01I tested it by injecting an external source 10MHz but still the same problem!if you have any information, thank you!73s

author: hendorog
author_rank: Super Contributor
timestamp: July 23, 2019, 10:01:10 am
content: Have you tried the marconi yahoo group. There are guys on there who know these inside out.https://groups.yahoo.com/neo/groups/marconi_test_instruments/info

author: RADIOAMAT
author_rank: Newbie
timestamp: July 23, 2019, 10:26:39 am
content: HiThank-You for your reply, i will post too, on this forum

author: RADIOAMAT
author_rank: Newbie
timestamp: July 23, 2019, 03:05:32 pm
content: I found the fault, no RST pulse of microcontroller 8085 on pin 9, coming from 4020 IC4 change it 4020Best regards
(Repaired) Marconi 2024 / 2023 RF Gen Error 508: Amplitude modulator Unlevelled - Page 1
Forum section: electronics / repair

author: RoadRunner
author_rank: Frequent Contributor
timestamp: September 22, 2019, 10:16:37 pm
content: I have recently bought a broken Marconi 2024 with LCD issue and Error 508: Amplitude modulator Unlevelled.I was reading to thishttps://www.eevblog.com/forum/repair/quick-repair-project-marconi-2024/old post on the forum and few people have attempted to repair Error 508. Forum post was really quite informative. But issue of Error 508: was appeared to be no solution. so i contacted forum member who have attempted to repair and got some information about what they findout in there attempt.Here my write up on my blog how i repaired my maroni 2024 Error 508:I am publishing link to my blog in the hope that someone having similar issue may get pointed to right direction.https://www.circuitvalley.com/2019/09/marconi-2024-2023-error-508-amplitude-modulator-unleveled-repair-fix.htmlRegards
Marconi 2380/2382 - Page 1
Forum section: electronics / repair

author: Squarewave
author_rank: Frequent Contributor
timestamp: December 23, 2021, 04:18:24 pm
content: Hello, I have a Marconi 2380 spectrum analyser with the 2382 RF unit.It has a fault that I think is a Data Link fault, according to the fault finding flow charts in the service manual.So I'm wondering if anyone here is familiar with these units and if anyone has ever had this fault before?The background:On power up, the lights flash on sometimes either one or both units, with the debug menu being on the screen. Following the flow charts, this suggests Data Link error. Looking over the Data Link charts, it suggests probing IC11 at certain pins and if not finding 20ms interval activity, then to follow the data link through from the 2382 into 2380 which I have done.During powerup a few days ago when I was going to make some tests, the SA burst into life and for that period of being switched on, appeared to work and function, which suggests to me that it isn't a fatal issue, perhaps poor connections somewhere? When I shut down and switched on again later on, it was back in the same fault. So I've cleaned PCB edge connectors, ribbon connectors external interlink connections and thru tested the interconnects, but the SA is still in fault.At this stage, all I can do is suspect one of three ICs until I know more.I wonder if anyone has any suggestions?Thanks.
Marconi 2955 black screen repair - Page 1
Forum section: electronics / repair

author: rachdatu
author_rank: Regular Contributor
timestamp: July 14, 2019, 11:23:59 am
content: HelloI was playing with my new GPIB interface when I noticed magic smoke coming out from my test equipment. I switched it off and took it apart. I was unable to locate where the problem was.After reading a few comments in different forums, I decided to first look at the 10MHz oscillator (OCXO).I removed screws holding the HV board, then I removed the grey plastic case covering the oscillator, unsoldered the small board (6pins) and took it on the workbench.I connected a 12 Vdc supply (current limited at 500 mA) at pin 4 and a 5 Vdc supply at pin 3, left the SYNC input floating and measured the frequency at pin 1 with my counter. GND is pin 2.The results didn't show anything wrong.Frequency nominal: 10MHzcold: drift +200Hzwarm (after 15 minutes): drift -500HzI resoldered everything back and decided to power up my 2955 with some precautions:external power supply set at 15Vdc and limited at 5A. You need that current to start this kind of equipment. After waiting a few seconds, I had to switch everything off. I "smelled" something around the HT coil...:-)I measured a few diodes and identified at least one faulty one; diode D9 (BA159) on AC1 board.I ordered them and added other components just in case like D14 (5.6 V Zener), TR3 (BU806 NPN transistor), D11 (MR854 diode), TR4 (2N2369 NPN transistor).A few days later, the items were in the mail box.I replaced D9, switched the external power supply on et voilà. Job done. CRT is back and I can proceed with my GPIB interface and some scripts...Some more pictures athttps://github.com/daturach/Documentation/wiki/Marconi-2955,-repair
Marconi 2955A - Fault when using Directional Power Heads  - Page 1
Forum section: electronics / repair

author: weejag
author_rank: Contributor
timestamp: October 31, 2022, 10:50:12 pm
content: I have a 2955A which I thought worked perfectly. All tests pass and the calibration is near perfect.I purchased the two variants (1-50MHz and 25-1000MHz) of the Directional Power Heads.I initially thought that they worked as they both gave reasonable readings on the CW setting.However, on switching to PEP there no power reading is obtained when applying RF to the Power Head. In fact a forward power reading of 620mW, or 940mW, or sometimes 0mW is displayed on the forward power. This reading does not alter when applying RF to the Power Head.I also discovered that when turning up the volume control a tone was present on the PEP setting (about 1.05kHz). This changes to a clicking or "motorboating" (about 2Hz) when switching to PEP.I tried both Directional Power Heads on another 2955 and they worked perfectly. They have intact seals and look unused (a military kit).I checked the DIN connecting lead and it seems fine (again military). I checked voltages:-Pin 2 - 12v Pin 7 - Not ConnectedPin 4 (Forward Power) - 0v on CW, 0.67v on PEPPin 5 (Reverse Power) - 0v on CW, -0.67v on PEPControl pins act as per the manual (H = 5v L = 0v) :-Pin 6 Pin 1 Pin 3H H L (CW)L H H (PEP)I have looked at internal connections on the accessory socket. I have also tried to investigate board AB/1 where the F/R power lines terminate but I'm struggling to find the problem.Having purchased the power heads I would like to have them working properly and would be grateful for any ideas as to how to proceed. Has anyone come across this problem before?Regards,weejag

author: George Edmonds
author_rank: Frequent Contributor
timestamp: October 31, 2022, 11:13:25 pm
content: HiYou are probably asking in the wrong place.Tryhttps://groups.io/g/Marconi-Test-Instruments.This is a dedicated support group for Marconi Instruments.G Edmonds

author: weejag
author_rank: Contributor
timestamp: October 31, 2022, 11:24:09 pm
content: Thanks.I'll try there too.Regards,weejag
Marconi 2955a RF signal generator problem  - Page 1
Forum section: electronics / repair

author: Proeletrotech
author_rank: Newbie
timestamp: January 24, 2023, 05:24:56 am
content: Hi guys, can someone help me? my marconi 2955 has this problem:The RF signal generator doesn't have frequency stability, I've put a external GPSDO on 1MHz input, but doesn't change anything, when you measure the frequency with a frequency counter, you cannot see any problems, but, when use a HF radio in SSB mode it's so clear the instability, I tested the HF radio with other RF signal generator and there's no problem at all.Does anyone already had this problem?Or a suggestion to solve it?Thanks.

author: George Edmonds
author_rank: Frequent Contributor
timestamp: January 24, 2023, 06:39:19 am
content: HiPlease keep in mind that the Marconi 2955, is it a 2955 or a 2955A, was never designed for use with SSB communications links, it’s primary role is for use with private FM radio links.It sounds that you are hearing phase noise from the Rx side signal generator, but from your description I cannot be certain. Without access to measurements from a modulation meter such as a Marconi 2305 or a HP8901/A/B it is impossible to say if the 2955/A meets its specifications or not.It is normal that if you listen to the 2955’s signal generator with a modern HF radio or HF transceiver you will hear all sorts of burbling noises.George G6HIG Dover UK

author: Kim Christensen
author_rank: Super Contributor
timestamp: January 26, 2023, 03:52:47 am
content: Not an insult, but just in case: Are you sure that it is in CW mode and all modulation is turned off?
Marconi 2955B CRT Issue - Can only see the extreme edges of the Geometry - Page 1
Forum section: electronics / repair

author: Reprobyte
author_rank: Regular Contributor
timestamp: June 13, 2023, 08:57:12 pm
content: Edit - Moved to Marconi boards as advised

author: George Edmonds
author_rank: Frequent Contributor
timestamp: June 13, 2023, 10:26:08 pm
content: HiYou need to be posting here.https://groups.io/g/Marconi-Test-InstrumentsThe Marconi Instruments support group on groups.ioG Edmonds

author: wasedadoc
author_rank: Super Contributor
timestamp: June 14, 2023, 10:54:47 am
content: The vertical scan appears to be upside down. Check vertical sweep generator, vertical output to deflections coils or plates depending on magnetic or electrostatic deflection.

author: Reprobyte
author_rank: Regular Contributor
timestamp: June 14, 2023, 02:04:28 pm
content: Quote from: George Edmonds on June 13, 2023, 10:26:08 pmThanks for the heads up George, I have moved the discussion over there.
Marconi 2955b wrong AF output level - Page 1
Forum section: electronics / repair

author: Armando1989
author_rank: Contributor
timestamp: January 26, 2022, 10:11:54 am
content: HiI have marconi 2955b test set. Passes all selftests.Problem is that output AF level does not correspond with setting... Level is much higher than set.. ie: set 400mv but output is 2.7vI tried follow service manual adjust Ab6 card R1 potentiometer till get correct voltage, however selftest fails on modulation 3.x selftests as the level is too low. I have to go back to the previous level to get selftests fine againFurthermore, manual states u can set af level to 1v while my 2955 cannot go so high in menu.Any ideas?ThanksBr

author: Armando1989
author_rank: Contributor
timestamp: January 26, 2022, 10:43:05 am
content: Solved, my faultIn "change parameters" menu it was configured as 20dB attenuator installed for bf (not the case) thus instrument was applying higher output accounting for the attenuation... Removing this setting allows select up to 1V and now output voltage is correct