Marantz PMD430 portable cassette recorder - No Audio - Page 1
Forum section: electronics / repair

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 05, 2022, 07:26:37 pm
content: I am having trouble with my Marantz. I have no output with the Line IN, Line Out, Microphones or tape playback. I do have the 4.5 volts and the 15 volts. I do get a mum from the internal speaker when I probe the playback volume control so I know the output amp is working. I am thinking the trouble may be in the muting circuit. I have attached the schematic. Since the sound affects both channels, it must be in a shared circuit.Any help would be greatly appreciated.schematic.pdf(3020.87 kB - downloaded 185 times.)schematic.pdf(3020.87 kB - downloaded 185 times.)

author: floobydust
author_rank: Super Contributor
timestamp: August 05, 2022, 08:02:57 pm
content: What do the VU meters, LED's do? In either Rec or Play.

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 05, 2022, 09:46:14 pm
content: The meters do not respond in playback or record. The Rec LED lights on record but the peak LED does not light up even though I had the record level high.The meter does indicate battery level when the button is pushed. The Left meter does show a slight movement if I inject a tone at the volume control terminal.I tried a microphone in the left and right mic inputs with no response.

author: floobydust
author_rank: Super Contributor
timestamp: August 06, 2022, 04:25:01 am
content: I first spend a minute or two look for fractured soldering joints, really common in portable gear.With so much not working, there are a few mute buses to check and it's a bit complicated.For playback it mutes on either STOP (QU03), FF/REW (QU04), PAUSE (QU02). The VU meters are also muted in STOP. Shorted capacitor CU02 2.2uF/50V at QU03 would leave muting stuck activated as if in STOP mode. Measure the three voltages on QU03 to see if it's on, causing the problem. QU03 collector goes high to activate muting. Or at connector JK02 to see the muting signals there from the PLAY, PAUSE, FF/REW switches.The mute switches areDTC124SOT-23 NPN digital transistor with built in resistors.

author: David_AVD
author_rank: Super Contributor
timestamp: August 06, 2022, 06:06:42 am
content: For old cassette player with a mechanical operated record function, always clean the record / play switch as they get dirty and oxidised with age and can cause no audio issues. Look for the long skinny switch that has a lever / wire from the record button.

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 06, 2022, 03:25:08 pm
content: Thank you for your help.I will try your suggestionsIn the meantime, I injected a signal into the L&R line inputs with the unit in record mode. I traced the signal to the P601 board. Nothing after the P601 board.I can't find a datasheet on the HA12048 which is a Dolby IC. I think the problem must be a shared component affecting the voltages since I don't have any signal on the line out jacks, microphone inputs or the tape head playback.I will check the components that were suggested.

author: fzabkar
author_rank: Super Contributor
timestamp: August 06, 2022, 07:50:05 pm
content: FWIW, there is a block diagram for the HA12046 and HA12047 Dolby ICs on page 7 of the following service manual:http://www.saabclarion.se/manuals/SaabClarion_86_ServiceManual.pdfThese ICs have the same pin count as the HA12048 ...

author: floobydust
author_rank: Super Contributor
timestamp: August 06, 2022, 08:30:05 pm
content: Can you measure the voltages at the P601 Dolby board connectors JK06, JK06. The +3.3V rail is alive? It's from QU01 and runs many IC's.I see it has a pesky DIN jack switch, it overrides the RCA jacks. Make sure that it is OK, as they never really get moved.

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 09, 2022, 09:29:11 pm
content: I found capacitor CL52 had a bulge at the top so I replaced it. I have ordered some other "suspicious" looking caps. I noticed on the schematic that CL52 (2200uf 16v) is in parallel with CL51 (2200uf 10v). I'm thinking they did this because of space limitations but why is one 10v and the other 16v? Maybe space limitations again. I will check the voltages suggested once I install the replacement capacitors.Thank you for your suggestions. I believe I'm on the right track.

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 12, 2022, 04:44:51 pm
content: Here is the voltages I measured in play.At QU03 : B 14.9v E 14.5v C 0v . I found the resistor RU03 which should be 220K was measuring in the megohms. Another 220K R712 also measured in the megohms. Other 220K resistors measured okay.Also at JK02 the voltages in play measured as follows:Pin 1 0VPin 2 4.6VPin 3 14.5VPin 4 0VPin 5 4.5VPin 6 14.6VPin 7 13.9VPin 8 12.8VPin 9 9.5VLet me know what you think. Thank you.

author: floobydust
author_rank: Super Contributor
timestamp: August 12, 2022, 05:35:05 pm
content: You can tell if a muting (logic) switch is turned on by the collector voltage at any of QU02, QU03, QU04. These are best to look at to see which if any of the 3 muting circuits are being turned on. You got 0V at QU03-C (stop muting) so it is off, good.JK02 pin 9, pause muting for QU02, looks low at 9.5V maybe check RU06 or QU02 is leaky. QU02-C should be around 0V when it is not muting for the pause button.

author: Smoky
author_rank: Frequent Contributor
timestamp: August 14, 2022, 02:34:58 am
content: A few years ago a bunch of used stereo gear was dumped in my lap. Two of these cassette decks were in the pile. One was apart so I stuffed all of its guts back inside and taped it up. Must have been a project at one time to get one of the two working since several service manuals and schematics came with them!

author: floobydust
author_rank: Super Contributor
timestamp: August 15, 2022, 04:10:07 am
content: I think it was for making bootleg tapes lol. List price 1986 was $599, it's got Dolby-B and dbx compander, three-head.Your Rev. 2 service manual might be worth scanning.

author: Smoky
author_rank: Frequent Contributor
timestamp: August 15, 2022, 04:06:45 pm
content: There appears to be three versions of the schematics for this tape recorder. The original copy that the OP has posted is from 1984, the revision is dated 1992, and the 2nd edition is dated 1996.Maybe the OP can post what the serial number is of his machine to see of it's after the serial number printed on the cover of the 2nd edition?If I can figure out which of the two tape decks that I have is in the best of shape, I'd be willing to part-out the other if you guys need some

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 15, 2022, 08:37:12 pm
content: Would you be willing to scanthe revised service manuals?

author: David_AVD
author_rank: Super Contributor
timestamp: August 15, 2022, 09:39:58 pm
content: If you do scan any audio manuals, please consider uploading them to HiFi Engine. It's a great resource.

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 18, 2022, 12:58:15 am
content: I replaced sever 220K resistors that were reading very high. I tested QU01, QU02 QU03 and QU04 in circuit using a curve tracer and they look okay.I still get no sound and now I don't get any hum when I probe around the volume control. Here are the voltages I took.At the collector of QU01 - 4.5VAt the collector of QU02 - 14VAt the collector of QU03 - 10VAt the collector of QU04 - 0VAt the pins of jack JK02:pin 1 - 0Vpin 2 - 4.5Vpin 3 - 14.3Vpin 4 - 0Vpin 5 = 4.5Vpin 6 - 14.3Vpin 7 - 13Vpin 8 - 13.6Vpin 9 - 0VI checked all the switches for Play, Stop, FF/Rew and pause - the are good and function correctly.The resistors RU02 thru RU017 and RU11 are good. It looks like Transistors are the only component left. They must be leaking?What are your thoughts?

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 18, 2022, 03:30:56 pm
content: I just got around the post concerning the voltages on QU01.I found that there is 0 volts on the emitter. It looks like the 3.3 volt rail is missing.I checked the transistor (2SD1020) in circuit with a curve tracer and it looked open. I removed it and checked it on my component tester and it read good.Again the curve tracer shows open. The only transistor I have is a NTE293. The NTE293 reads good on my component tester and good on the curve tracer.I hesitate to use the NTE293 because it is not an exact match and the Marantz schematic shows this as a critical component.I don't read any shorts on the emitter connection with the transistor removed.Is there a better substitute for the 2SD1020?

author: Smoky
author_rank: Frequent Contributor
timestamp: August 18, 2022, 04:49:25 pm
content: Here's the latest schematic from the 1996 2nd Edition service manual

author: wasedadoc
author_rank: Super Contributor
timestamp: August 18, 2022, 06:36:25 pm
content: Quote from: Bargainhunter on August 18, 2022, 03:30:56 pmQU01 is not critical, the Zener DU01 is.What voltages are the collector and base of QU01?

author: floobydust
author_rank: Super Contributor
timestamp: August 18, 2022, 08:00:33 pm
content: Missing the 3.2 or 3.3V rail would make the deck pretty quiet with no power to the audio IC's. QU01 is the 3.3V reg, beta >200 not sure how much current it supplies, highest during record. If it runs hot then there's a short -circuit downstream. Your curve tracer might not be dependable if it says it's open but it's not? The part might be fine.NTE253 is big TO-92 tall compared to the 2SD1020. I like Zetex E-line parts like ZTX690B BUT they have different pinout EBC ve ECB and hard to get in the semi shortage. You could try the NTE253 to see if it makes a difference temporarily. CU01 1,000uF 6V might have shorted, you can measure the voltage drop across RU01 100R.JK02 pin 9 goes low when the Pause button is pressed, which turns on mute switch QU02. QU02 collector high at 14V means it's on and muting in Pause mode.JK02 pin 8 goes low when the Stop button/Auto Stop is pressed, which turns on mute switch QU03. QU03 collector high at 10V means it's sorta on and muting in Stop mode. CU02 leaky, RU03 I think you replaced, and otherwise it's a bit of work to troubleshoot this.So I'd leave the muting stuff for later, first get the 3.3V rail up and working.Smokey thanks for the scan. These PMD430 tape decks were out for at least 10 years, pretty impressive for a portable model.

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 18, 2022, 09:21:55 pm
content: First let me thank Smokey for the scan and everyone who posted.The voltages at QU01 are Base 3.2 volts; Emitter 0 volts and Collector 4.4 volts. I removed transistor Qu01 and got the same voltages so I re-installed QU01 and lifted the Emitter from the circuit. I was thinking QU01 acted like a switch but still got 0 volts on the emitter. I found out that there has to be a load or drain on the emitter for the transistor to turn on. I get in the meg ohms when I measure on the circuit board where the emitter should be connected and the ground. RU01 (100 ohms) measures good.So with all the IC's connected to the emitter of QU01, I should see some sort of load or am I barking up the wrong tree? I'm thinking an open jumper or trace on the board.Also zener ZU01 with a 1N4730. I'm not sure why I reading 3.2 volts instead of 3.9 volts. I also replaced CU01 - with a 1000uf 10v instead of a 1000uf 6.3v. The 10v is too tall so I have to order the 6.3v. I still got the same reading with ZU01 and CU01 replaced. I also tacked in NTE293 and got the same voltages with 0 volts at the emitter.It's probably something simple that I'm overlooking. Thanks for all your help.

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 18, 2022, 09:25:19 pm
content: I also see that the emitter of QU01 goes to the headphone jack and is connected to ground thru a 4.7k resistor when headphones are plugged in. Could this be a factor?I don't see how all the IC's on the 3.3v rail are open.

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 18, 2022, 10:27:48 pm
content: Update: I have no circuit from emitter to pin 5 of JK03. It is very hard to follow the traces since it is a double sided board with thru-holes and components covering the traces.It would be nice the see an unpopulated circuit board to show the traces. There has to be a break somewhere on the board.

author: wasedadoc
author_rank: Super Contributor
timestamp: August 18, 2022, 10:50:22 pm
content: Quote from: Bargainhunter on August 18, 2022, 10:27:48 pmPin 5 of JK03 goes to the collector of QU01, not its emitter.If you have the base and collector legs of a good transistor connected with a few volts on its base and about 4.5 on its collector and its emitter not connected to anything except your test meter, you MUST have almost the same voltage on the emitter as its base.

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 18, 2022, 11:30:59 pm
content: Thank you for your reply.My schematic clearly shows pin 5 connected to the emitter of QU01. It's the symbol with the arrow pointing away (NPN). Please double check and let me know if I'm wrong.Also pin 5 is connected to ground. It does not show that on the schematic but I have attached a photo of the pc board. I drew a red line indicating a jumper wire from pin 5 to the case leg of switch S702. One of the four mounting legs goes to ground. Should this jumper be attached here?

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 19, 2022, 12:07:05 am
content: Thank you for your help.My schematic clearly shows the emitter of QU01 going to pin 5. The symbol shows the arrow pointing away as in a NPN transistor and is going to pin 5. Could you double check your schematic and let me know if I'm wrong. Also I traced pin 5 on the circuit board and it is connected to ground by way of a jumper going to one of the mounting legs of switch S702. I've attached a photo with a red line showing where the jumper is attached. Wouldn't this cause the 3.3 volt rail to be 0 volts on all connections to QU01's emitter?

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 19, 2022, 12:08:28 am
content: Sorry, I forgot to attach the photo.

author: wasedadoc
author_rank: Super Contributor
timestamp: August 19, 2022, 12:09:00 am
content: I'm using the schematic posted by Smoky. Se my trace in red.I still think you problem is around QU01. What is your response to my "MUST" statement above?

author: wasedadoc
author_rank: Super Contributor
timestamp: August 19, 2022, 12:19:54 am
content: On the board photo, JK03 contacts are numbered 1 to 7 from left to right. Your red line is from pin 3, not 5.

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 19, 2022, 12:41:32 am
content: Thank you, thank you thank you. wasedadoc. I did not see that! On the my schematic (attached) the pins are left to right 7 to 1 and on the photo of the pc board, the pins are left to right 1 to 7. That totally confused me. So the jumper wire is correct. I agree with your "MUST" statement. Take a look at the schematic I attached. QU01's collector and emitter is reversed from smokey's schematic. Is my service manual wrong? Where can I download the full service manual like Smokey's?I agree with you that the problem is with QU01. I have no 3.3 volts going to the IC's I wonder if QU01 was installed backward. That would mean the Base on Emitter were reversed. The two schematics have the Emitter and Collector reversed. [ Attachment Invalid Or Does Not Exist ]

author: wasedadoc
author_rank: Super Contributor
timestamp: August 19, 2022, 01:02:10 am
content: You have not attached your schematic. If yours has emitter and collector swapped compared to Smoky's then yours is wrong. That voltage circuit could not work if different from Smoky's schematic.

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 19, 2022, 01:12:21 am
content: Attached is the my schematic. [ Attachment Invalid Or Does Not Exist ]

author: wasedadoc
author_rank: Super Contributor
timestamp: August 19, 2022, 01:14:15 am
content: Quote from: Bargainhunter on August 19, 2022, 01:12:21 amNothing attached.

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 19, 2022, 01:14:51 am
content: I don't know why my attachments are not working.I will try again

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 19, 2022, 01:18:51 am
content: Here is the full schematic.

author: wasedadoc
author_rank: Super Contributor
timestamp: August 19, 2022, 01:28:47 am
content: Not a case of collector and emitter swapped. Slightly different design. Your schematic has the 3.3 Volt point going to pin 5 and Smoky's has the 4.5 Volt supply going there. You need to do a continuity check on your board to see which of these is the case.1. There was a design revision. Your board corresponds to your schematic.2. There was a design revision. Your board corresponds to Smoky's schematic.3. There was only one design. Your schematic is correct.4. There was only one design. Smoky's schematic is correct.

author: wasedadoc
author_rank: Super Contributor
timestamp: August 19, 2022, 01:35:28 am
content: Long, long past my bedtime here.

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 19, 2022, 01:39:20 am
content: Thank you for all your help.I will check out the circuits to see which is correct.I have to find out why the 3.3 volts is missing.I'll let you know what I find out in the next few days.

author: Smoky
author_rank: Frequent Contributor
timestamp: August 19, 2022, 02:46:20 am
content: Bargainhunter, If you open the battery compartment to your tape deck, the serial number should be printed on a piece of tape. Let us know what it is.

author: wasedadoc
author_rank: Super Contributor
timestamp: August 19, 2022, 11:33:36 am
content: A difference between the two schematics is that on Smoky's the four LEDs DX01, DX02, DX11, DX12 are powered by the 4.5 Volt side (collector) of QU01. On the other schematic all those points are fed from the 3.3 Volt side (emitter) of QU01. If that was a deliberate design change I would have expected the resistors in series with the LEDs to have been changed to maintain their brightness levels but they are not.Another difference is RX01. In Smoky's schematic that 220 ohm resistor is on pin 4 of WX01. In the other schematic it is on pin 5 and in series with all the LEDs. That would mean that the brightness of each LED would depend on what other LEDs are on. That doesn't look right.I think Smoky's schematic is correct and the other one is not a different design version but just has drawing errors.But whichever that doesn't address the issue of QU01 emitter not being anywhere near 3.3 Volts.

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 19, 2022, 01:29:21 pm
content: Thank you for all your help. I ordered some 2SD1020 transistors. When I receive them I will set up a breadboard and duplicate the circuit with QU01, DU01 zener, CU01 1000uf 6.3v and RU01 100 ohm resistor. If I apply 4.5 volts to the collector, should I get 3.3 volts on the emitter or would I have to apply a load from the emitter to ground to turn on the transistor?Smokey: The serial number is 69U270242. I hope this helps.Thank you.

author: wasedadoc
author_rank: Super Contributor
timestamp: August 19, 2022, 02:11:32 pm
content: The transistor is not used as a switch. It is used as an emitter follower, essentially providing the same voltage (less the 0.6 Volts Vbe drop) as the zener but with greater current capability.There is no need to duplicate on a breadboard. That circuit is absolutely standard and well understood. Duplicating it will merely confirm that it works. Instead do this.1. Put the QU01 that you have back in the board except its emitter leg. Emitter not connected to anything.2. Power up.3. Measure and note down the voltage at its collector.4. Measure and note down the voltage at its base.5. Measure and note down the voltage at its emitter.6. If the emitter voltage is zero or lower than (base voltage - 0.6) then QU01 is faulty. Replace with another NPN or SD1020 if available. Go back to step 1.7. If you are at this step the emitter is somewhere between 2 and 4 Volts.8. Power down.9. Leave the emitter connected to only the positive lead of the meter.10. Switch the multimeter to measure current. If not an autoranging meter select 200 mA range.11. Connect the negative lead of the meter to the board where the emitter would normally be connected.12. Power up and operate playback.13. Measure and note down the current.14. Power off.15. Disconnect meter and switch it back to measuring voltage. Switch it off.16. Post back here with all the noted down measurements and whether you had to replace the transistor to get to step 7 and whether audio was heard at step 12.

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 19, 2022, 02:36:54 pm
content: Thank you wasedadoc. I really appreciate your help.I did try lifting the emitter of QU01 and got 0 volts. I removed the 2SD1020 and tacked a NTE293 in its place with the emitter lifted and also got 0 volts. Since the NTE 293 is not an exact replacement, I ordered some 2SD1020's off ebay. I should have them in a few days.I will try your recommendations and get back to you.

author: wasedadoc
author_rank: Super Contributor
timestamp: August 19, 2022, 02:57:58 pm
content: Quote from: Bargainhunter on August 19, 2022, 02:36:54 pmFor the emitter lifted voltage test you don't need an exact replacement.AnyNPN transistor in that test with a few volts on its base should give much more than 0 Volts. Either your NTE293 is also faulty or you are doing something wrong with the way you are connecting/measuring.

author: floobydust
author_rank: Super Contributor
timestamp: August 19, 2022, 04:29:48 pm
content: I agree, you're missing something and should not get 0V on the emitter, especially with a new transistor which indicates the transistor is not the problem.You can measure the voltage across the zener/cap as around 3.9V for the base. If it's 0.7V with the emitter at 0V, then it will be getting hot...

author: floobydust
author_rank: Super Contributor
timestamp: August 20, 2022, 12:46:28 am
content: Quote from: Bargainhunter on August 19, 2022, 09:04:18 pmUh your post ended up in the wrong threadhttps://www.eevblog.com/forum/repair/need-help-sourcing-stainless-steel-crimp-on-ring-or-lug-terminals/msg4368601/#msg4368601

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 20, 2022, 12:54:47 am
content: Now I'm getting somewhere. I wired up the 2sd1020 transistor, the zener the 1000uf electrolytic and the 100 ohm resistor as in the diagram and BINGO, I got 3.5 volts on the emitter. I tried the NTE293 and also got 3.5 volts on the emitter. So now I'm getting someplace. I couldn't solder the 2sd1020 or the NTE293 on the circuit board with the emitter lifted because I had a couple traces starting to lift because of the soldering and de-soldering. I also have the 1000uf electrolytic off the board because I didn't have a 6.3v electrolytic to solder on the board. The original cap was bulging. I used a 10v 1000uf to do the testing but it is too large to fit on the board. I have some 6.3v caps on order and they should arrive tomorrow or Monday. I will then test the transistors on the board with the emitter lifted and measure the voltage. If I don't get 3.3 volts, then I know there is a problem with a connection on the circuit board or a component on the board.

author: wasedadoc
author_rank: Super Contributor
timestamp: August 20, 2022, 09:08:04 am
content: 1. That bit of circuitry is not sensitive to component layout. To make troubleshooting and measuring easier you can solder some wires to the solder side of the board and have the transistor at the other ends. Even wires a few feet long would be OK.2. The capacitor is not essential for circuit operation. Zeners are noisy devices and it is standard practice to put a capacitor across them. Yes you should have a capacitor there for the final repair but you can troubleshoot and get audio working without any capacitor there.

author: Smoky
author_rank: Frequent Contributor
timestamp: August 21, 2022, 05:04:23 am
content: Since I have two of these tape decks, I thought I would de-solder one or two of the 96 electrolytics buried in each of these things. So the very first one I checked was on the Meter/LED board (PX01).Would you believe, it appears to have been installed backwardsWhat are the odds of that!Sure enough, the (-) side of the 10uf/16v capacitor (CX01) goes straight to pin 10 of the LC4011B (QX01).All I can say is, thank goodness I have ten other projects I haven't finished from last yearBack in the box these go!

author: floobydust
author_rank: Super Contributor
timestamp: August 22, 2022, 01:57:18 am
content: You'd have to confirm the silkscreen but that cap sees both polarities and it's just the backlight latch. Normally it's backwards polarity? unless the backlight is on, so maybe they flipped it.I have a Sony TV remote with the 100uF electrolytic capacitor in backwards, it didn't mind -3V it seems.

author: Smoky
author_rank: Frequent Contributor
timestamp: August 22, 2022, 04:03:11 am
content: Grab the fire extinguisher Floobydust!I went looking for QU01 in this tape deck to see how she looks and...Holy bolts of lightning Batman!

author: floobydust
author_rank: Super Contributor
timestamp: August 22, 2022, 07:08:04 am
content: EEK! That transistor powers most of the universe- all the Dolby and DBX IC's. It would take a 'smoke it out' strategy to find the short and even then the IC's are surely rare.

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 22, 2022, 09:57:07 pm
content: This makes no sense to me. I received the 2SD1020 transistors today. I soldered the new 2SD1020 on the board and measured thlie voltages.I got Base 3.2V, Collector 4.5v and Emitter 0V. I lifted the emitter and still got 0V. I took the transistor out and tested it on my component tester and it tested good. I made sure I inserted the transistor on the board the correct way. Then as suggested, I soldered three jumper wires to the board and connected the transistor and got 0V on the emitter. I grabbed a NTE 293 transistor and connected it to the jumper wires and measured the voltages. I got Base 3.2V, Collector 4.5V and with the Emitter not connected, I read 4.5V on the Emitter. I connected the Emitter to the jumper and still read 4.5V. Shouldn't I have 3.2 volts on the Emitter? Also before I got a hum on the speaker when I touched the contacts of the volume control even though I had no playback or signal on the line in or line out. No I get silence. Why is the NTE293 reading voltage on the Emitter and the 2SD1020 not reading any voltage in or out of circuit?

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 22, 2022, 11:14:42 pm
content: I connected my meter between the emitter and the circuit to measure the current and I measured zero current draw on the emitter of 2sd1020/net293. I must have an open circuit or the IC's are bad. If I insert a headphone plug, I do measure 4.7K from the emitter to ground so I do have a complete circuit to R715 going to the headphone switch.I will have to trace the circuit to pin 11 of Q907, pin 22 of Q809and RG54. I'll let you know what I find out.

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 23, 2022, 01:08:05 am
content: Latest update:I had an open circuit and I traced it to the contacts on RG54. I re-soldered the connections around RG54 and now I've got voltage on RG54, Pin11 of Q907 and pin 22 of Q809. I only measure 2.8 volts on the emitter of QU01. Also as suggested I measured the current flow from emitter (lifted) to the pc board and got no current flowing from the emitter. Also I still get no sound although the motor is running.

author: floobydust
author_rank: Super Contributor
timestamp: August 23, 2022, 07:10:17 pm
content: Is QU01 running hot? It doesn't make complete sense what you are seeing- good transistor but low emitter output voltage.When you get 2.8V out, what are the base and collector voltages? Just to narrow down if the regulator is not working, or it is but just overloaded.

author: Smoky
author_rank: Frequent Contributor
timestamp: August 24, 2022, 01:52:37 am
content: Hey Guys, here's what I found in the second tape deck. The QU01 area looks good on both sides of the board:But, not so much in other areas. Look at some of the repair work I found:Bargainhunter, I don't plan on repairing either of these decks. So if you live in the USA, I'd be willing to send you what parts you may need. I plan on buying my first hot-air station next month so removing IC's will be easy. I do own a Huntron Tracker and a Peak Atlas semiconductor analyzer to check stuff too

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 24, 2022, 02:06:43 am
content: Hi Smokey,Thank you for the offer. I live in Pennsylvania.If you are looking for a hot air station, I'll trade you for the PMD430s. The hot air station is a model 858 and in like new condition.Let me know.