Yaesu FRG-7000 Communications Receiver Restoration - Page 1
Forum section: electronics / rf-microwave

author: xrunner
author_rank: Super Contributor
timestamp: December 27, 2019, 02:01:21 pm
content: I got this unit from a ham friend who got it at a ham fest. he asked if I wanted it, I could just pay him the same that he gave for it. After I got it home I gave it a quick check-out, and it seemed to be in fair condition. Dirty and needing an alignment. But after looking at stock photos of this radio I noticed something was not right. Someone in the past had replaced three of the original knobs with the wrong ones. I don't know if the originals got broken or some kid did it because they thought it looked cool. After I saw that I had just put it away to see if any knobs would become available on Ebay.So far no knobs for this radio have shown up, and from what I see Yaesu didn't use these knobs on any other radio. So I decided to try and create the original knobs and 3D print them. You can see what the originals look like in the second photo of a stock radio. The knobs that were replaced had set screws, but I don't think that will be necessary to have. Two of the knobs are on a "D" shaft and do not need a set screw. The other one, which is a volume control, I'm not sure about. You can see at the end the shaft has a slot cut. Is that an insertion point for a nib in the end of the original knob? I don't know yet about that, I'll cross that bridge when I come to it.First I'm going to design the other knob which shouldn't be too hard, and is duplicated twice, one for the band and one for the mode. The diameter is easy to get from the indented hole in the radio, but the other dimensions will have to be approximated from the picture. The knobs are black and I already have that color PLA. I can paint the white line on easily.

author: German_EE
author_rank: Super Contributor
timestamp: December 28, 2019, 10:20:45 am
content: Nice, not seen one of those for a few decades. Do they use a Wadley Loop for tuning or is it a synthesizer?

author: PA0PBZ
author_rank: Super Contributor
timestamp: December 28, 2019, 10:33:42 am
content: Quote from: German_EE on December 28, 2019, 10:20:45 amIt has a separate MHz knob, that's a typical indication that it is a Wadley.

author: xrunner
author_rank: Super Contributor
timestamp: December 28, 2019, 01:14:22 pm
content: Quote from: German_EE on December 28, 2019, 10:20:45 amIndeed as PA0PBZ stated is uses the Wadley Loop System. It has the basic modes - AM, USB, LSB, & CW. AM filter is 6 kHz and the SSB filter is 3 kHz. It is a standard fair receiver but has good reviews on eHam.I made a lot of progress on the first knob design which is for both the band and mode. I got the basic design down and had to play with the shaft hole diameter but I got a great fit now. Today I need to add the fill-in for the D-part of the shaft so it will fit even better (and print in black).After the knobs are done I will proceed to a full cleaning and alignment, I do have a service manual.

author: xrunner
author_rank: Super Contributor
timestamp: December 29, 2019, 02:21:03 pm
content: Finished the new knobs. I went ahead and designed-in set screws too. Painted on a white strip, looks acceptable. Better than the bastardized knobs somebody slapped on it.But, some bad news. I was playing with an alignment on the RF unit and two of the ceramic trimmers broke. The insulating disc that has one of the plates just cracked the first time I tried to turn them - probably never been touched since the factory. There is one trimmer and one coil for the input for each band. That's how these things go with 40-50 year old electronics. So now I must source replacements.

author: xrunner
author_rank: Super Contributor
timestamp: December 31, 2019, 02:45:41 pm
content: And another issue ...Ever since I got this radio I noticed that an AM signal never tuned in properly regarding peak signal vs. it's correct frequency. No matter what band, the freq. readout was always ~2 - 3 kHz low. I assumed the reference was just off a bit and went on to other issues.Well, after a lot of adjusting going through the service procedures, the readout was still off the same amount tuning AM signals. However, some testing with SSB (using the ceramic filter used in that path) revealed correct frequency readout vs. a known SSB emission.In the past, someone had replaced the stock AM filter (NTKK LF-C2A 6 kHz) with another type that I believe is a 4 kHz bandwidth (MuRata CFS-455I). It isn't unusual to replace stock AM filters for a tighter BW. In order to install it, it had to have pigtail wires put on its pins and mounted under the PCB using the holes for the original filter.They also put in a mod with a switch mounted on the back that allowed one to use the SSB filter for AM. When this filter is used for AM, the signal is tuned correctly centered (but the bandwidth is very narrow of course).So I did a sweep of both filters and, as you can see, the original SSB filter is centered in the passband, and the modded AM filter is not. Now I need to find another AM filter, the list grows ...

author: xrunner
author_rank: Super Contributor
timestamp: January 03, 2020, 01:38:08 pm
content: Well I got some replacement trimmer caps and replaced the three that broke (2x40 pF, 1x20 pF). Need a couple more because I want to replace all of them now, so had to order another set.Been fighting another mystery issue which was observed even before replacing the trimmers. I got all the preselector coils and trimmers (the area I was working in) aligned but I have a mystery. For example, band C goes from 1.6 - 4 MHz and band D from 4 to 11 MHz. If you set the signal generator to 4.0 MHz, and switch bands from C to D, and retune the preselector from one end to the other (because 4 MHz will now be at the other extreme) the signal is the same strength. That is as it should be.But if you do the same thing for 11 MHz, which will be at one end of band D and the other end at band E, the 11 MHz signal is drastically lower on band E. No amount of retuning the pre-selector components that I've done (and I've done a lot) can make it anywhere the same strength as when it is tuned in on band D (see pics). There is no difference in any active rf components upstream (same rf preamp and so on). The only change is the coil and trimmer set change (from TC04/T04 to TC05/T05) and the band switch position (I have put contact cleaner in the band switch). The farther up in frequency you go on band E, the better the signal strength. All alignments have been done with the sig gen set to -73 dBm which is an agreed upon level for an S9 signal in the HF bands.As far as I can tell now the receiver is operating well in all other areas. I just want to get past this mystery now. It may be a marginal design and not much I can do about it. Any ideas are welcome.

author: xrunner
author_rank: Super Contributor
timestamp: January 04, 2020, 07:10:57 pm
content: All problems lead now to the band switch -Taking a break from the previous issue, I turned to a quick alignment (or so I thought) of the low bands, that being 250 - 550 kHz and 550 - 1600 kHz. However, no signal was getting through from the ant. input. After the troubleshooting for that, it was determined that the signal for those bands was not making it through the band switch. Inspecting the switch revealed that it was able to be disassembled. Having already applied Deoxit and seeing no other way to clean the innards, I decided to man-up and go for the disassembly.Making careful notes, I was able to pull each section apart. Each section had a center holder that held two tiny metal spring contacts that made the connection from one side to the other for each of the three sections. Very carefully placing these parts in cups, I inspected each section. This revealed some very bad tarnishing that could explain the loss of signal on the low bands. Also, the springy contacts need to have some spring put back into them by some slight bending. I also now believe that this bad tarnish accounts for the previously explained alignment issue with 11 MHz.I'm going to carefully polish each ring and contact taking as long as I need to, then try to put it all back together.The fun never ends ...

author: xrunner
author_rank: Super Contributor
timestamp: January 06, 2020, 12:05:42 am
content: I got the switch all polished up and put back together ... and although it needed cleaning, that did not solve the problems.But it led me to the promised land. After more troubleshooting I determined that one of the 3-sections in the variable capacitor used in the pre-selector measured zero capacitance. They all should track from zero to 335 pF. On the lowest band (0.25 to 550 kHz) all three sections are required for a resonant condition and for one section to have zero capacitance caused the issue.The pre-selector capacitor is pretty much buried in the radio, but I had no choice but to tear it out and inspect it. It may be hard to see, but the bottom section definitely has white powder on it indicative of aluminum corrosion. The plates in this part are very, very close together and I need to clean all the corrosion out.Any cleaning suggestions would be appreciated.

author: 9aplus
author_rank: Regular Contributor
timestamp: January 06, 2020, 09:16:00 am
content: My first guess after looking on your schematic was short circuit on main variable C....Try with compressed air and thin razor blade, each side on full open C.After, inspect with magnifier glass and check with ohm meter range on each section turning full turn range.GL

author: PA0PBZ
author_rank: Super Contributor
timestamp: January 06, 2020, 09:33:13 am
content: On the lower band the 3 sections are in parallel, so if there was a short in one of the sections they would all have been shorted, and since all sections use a common connection to ground that can't be the problem either. I think the oxidation is another red herring.

author: xrunner
author_rank: Super Contributor
timestamp: January 06, 2020, 01:10:14 pm
content: Quote from: PA0PBZ on January 06, 2020, 09:33:13 amTo confirm there was a problem (some problem I am not saying a short) , I got a 220 pF cap from my box and set the other two sections to 220 pF (they track from 0 to 335 pF). I then observed what frequency the low band (220 to 550 kHz) would be resonant on the preselector scale (it was about 520 kHz). I then de-soldered the bad section and soldered the 220 pF cap in place of that section. So at that point they are all set to the same value as they would be normally. At that point, I was able to receive the test signal on the radio, where I never did before.In any case, the thing is disassembled and I will now clean it with some tuner cleaner and put it back in the radio if its working, and keep pushing ahead.

author: xrunner
author_rank: Super Contributor
timestamp: January 07, 2020, 01:37:08 pm
content: The pre-selector components have been cleaned with "Misty" contact & circuit board cleaner, and it has been re-installed. Now the lower two bands work OK.As far as the 11 MHz issue between bands, I asked a person on another forum who has aligned this radio, whether it was normal operation for this radio, and he said yes, so it's working "as designed" not "as desired".Now everything it seems is on-par except for the replacement of the 455 kHz filter, which I received yesterday in the mail. this morning I'll sweep it to make sure it is centered, and remove the one installed under the PCB. Then since this one is small enough, I'll install it on top of the PCB where the original one would have been install - dead bug style.

author: xrunner
author_rank: Super Contributor
timestamp: January 11, 2020, 11:30:07 pm
content: The new 455 kHz filter didn't make much of a difference. It's not shifted as bad but still is. An AM station still seems like it wants to be tuned off about ~ -1 to -2 kHz. As I said before, SSB signals don't seem to be tuned off frequency (SSB uses a different filter about 2.4 kHz). I re-checked the entire alignment but there was nothing wrong. I did an experiment to confirm my radio alignment was OK.I wanted to receive some AM signals but use the narrower factory SSB filter. Instead of de-soldering the SSB/CW filter and placing it in the AM path I swapped the control lines as shown in the attachment. That way when the radio is placed in AM mode it will use the SSB filter (which is too narrow for normal AM listening but OK for this tuning check) and won't have the BFO frequency active. When I do that, the AM signals are spot-on and tuned exactly to the correct frequency and the S-meter is highest reading).So, I do not think I yet have a decent AM filter and I need to continue to look for one (the CF01 part in the schematic). I would prefer the original but I can't locate one (NTKK LF-C6).I can now turn to some of the cosmetics. I soaked the faceplate in warm soapy water and it now looks 100% better. The knobs and feet will be cleaned in an ultrasonic bath. The cabinet also will be washed. None of the cabinet screws were the correct black screws and were not metric threads, but instead were imperial and it's a wonder they didn't strip out the threads. I ordered a new set of black M3 screws. In addition a new SO-239 coax connector is coming.Also needed is a replacement of the narley strap handle. What I did was to go to the local thrift shop and get a $2 leather belt. I cut it to length and was able to work the metal strap through the middle of it. I will then cut the holes in the ends and it should be OK.The project continues ...

author: German_EE
author_rank: Super Contributor
timestamp: January 12, 2020, 09:29:29 am
content: Well done on the leather belt trick, good idea.

author: xrunner
author_rank: Super Contributor
timestamp: January 12, 2020, 03:29:39 pm
content: Quote from: German_EE on January 12, 2020, 09:29:29 amThanks, but it really wasn't my idea, a friend suggested it.Couple more pics for now -

author: xrunner
author_rank: Super Contributor
timestamp: January 14, 2020, 02:52:50 pm
content: Found an interesting situation. In the actual radio the rf amp (Q101) and the 1st IF (Q104) are swapped according to the circuit description and the schematic. In the actual radio the rf amp is a 3SK40 and the 1st IF is a 3SK51. This is reversed according to the circuit description and the schematic, BUT according to the block diagram BOTH are supposed to be 3SK51.In the previous radio they produced which uses a lot of the same circuitry (FGR-7), both these components are 3SK40.Need to check some data sheets.

author: tkamiya
author_rank: Super Contributor
timestamp: January 15, 2020, 05:55:47 pm
content: About display disagreements between AM and SSB filter.....For AM, the frequency displayed is always the carrier frequency. However, I believe for SSB, no such standard exists. I *think* ham rigs usually read the frequency of side band, and military gear usually reads the carrier that has been suppressed. That means there needs to be some shifting going on....I'm sort of guessing that might be the issue.

author: Grandchuck
author_rank: Super Contributor
timestamp: January 15, 2020, 06:02:34 pm
content: The bandwidth of the sideband is about 3 kHz ... so how can this work (I guess you could set an arbitrary audio tone such as 1 kHz)?Seems that the suppressed carrier frequency makes the most sense.

author: xrunner
author_rank: Super Contributor
timestamp: January 15, 2020, 06:32:57 pm
content: Quote from: tkamiya on January 15, 2020, 05:55:47 pmYes tkamiya, I am fully aware of all that. Yes an AM signal will tune center freq. as the dial indicates, as the "advertised" transmit freq. and the signal will be maximum. Read my earlier post where I swapped the AM and SSB filters to prove that the AM filter still needs to be replaced in this radio.QuoteHam rigs (I am a ham myself) tune an SSB signal where the (non-existent) carrier would have been. For example if I tune my radio to 14.300 MHz and the mode to USB, then I will hear any transceiver transmitting in USB when he sets his radio to 14.300 MHz. All the emissions will be above 14.300, and below 14.300 MHz if LSB. If it's not an "old" radio that's transmitting, then I do not have to tweak my tuning, the voice will sound normal. If he changes mode to AM, then I do not have to re-tune at all - I stay at 14.300 MHz.

author: tkamiya
author_rank: Super Contributor
timestamp: January 15, 2020, 07:56:31 pm
content: If you look at old side band rigs, for example TS520S, you see 3 lines above the main tuning dial. Center, right, and left. They are spaced 1.5KHz apart. A3 (AM) sorry, old designation... I don't know the new ones) is 6KHz wide, A3J (SSB) is 3Khz wide. So, it's right in the middle of A3J mode voice bandwidth. One side is LSB, the other side is USB.https://www.universal-radio.com/catalog/hamhf/ts520lrg.jpgSo, yes, you don't have to touch the dial but where you are tuned are 3KHz apart from USB to LSB. Newer rigs don't have 3 lines. That would mean it is electronically adjusting the vfo. What I am suggesting is, that function may be stuck or flipping wrong somehow.Fixing older ham radio rigs are my second hobby. Having relay stuck or contacts tarnished so bad it doesn't make good connection is very common. I read your post about swapping filter. A point I'm trying to make is, slightly different. If it helps you, great. If not, please ignore. I never owned that particular radio. I lusted over FRG-7 though. Good luck.I am a ham as well.

author: xrunner
author_rank: Super Contributor
timestamp: January 28, 2020, 12:03:03 am
content: Latest updates:I had ordered a 3SK51 dual-gate MOSFET to see if it was better than the 3SK40, due to disagreements in the documentation, just to see what would happen. However, it did not perform as well in testing, so I re-installed the 3SK40 as the RF amp. There is one more device I am going to try as an experiment - a 3N211. This is documented by others as a better replacement for the 3SK40 as an RF amp, so we'll try another round of tests when I get it.I started on some of the cosmetic restorations. I completed the replacement handle which uses an old leather belt I got from the local thrift store. It worked out well. I washed the metal cabinet in the bathtub, and then applied a coat of carnuba wax to the old paint on the cabinet, and this made it really pop out and shine. I also re-painted by hand the silver stripe that goes around the front panel because it was worn from use.More to come.

author: xrunner
author_rank: Super Contributor
timestamp: January 28, 2020, 11:30:39 pm
content: Front panel completed with knobs -

author: xrunner
author_rank: Super Contributor
timestamp: January 29, 2020, 11:37:56 pm
content: Well ... now the front panel is all coming back off. One of the indicator bulbs in the time display cluster went out.I don't have any grain of wheat bulbs that are rated for the VCC voltage they are using (8V). I do have 6V bulbs:6V bulb = 9.6 ohms8V bulbs (in system) = 22.6 ohmsAll of the bulbs are tied together to VCC, and each one is turned on individually, only one is on at a time. So, I think I'll just replace the four bulbs with new 6V parts and put a current limiting resistor in around a value of 13 - 20 ohms or so.(yes I could replace with LEDs but I'll try to stick with vintage for now)

author: xrunner
author_rank: Super Contributor
timestamp: February 02, 2020, 10:22:55 pm
content: The FRG-7000 restoration project is now finished. I hope that by posting this thread someone in the future will find it helpful.Thank you for following.

author: Klondike Mike
author_rank: Newbie
timestamp: January 23, 2021, 03:50:43 am
content: Quote from: xrunner on February 02, 2020, 10:22:55 pmReally? Have you replaced any electrolytics?https://klondikemikescapkits.com/products/yaesu-frg-7000-electrolytic-capacitor-kit

author: radiojack
author_rank: Newbie
timestamp: September 18, 2021, 06:01:46 pm
content: hello, I have read this thread with interest since i have recently bought a FRG-7000The FRG-7000 which appears to be working but since I just recently bought it off ebay I thought I should check the alignment.In the manual there is only 1 page for maintenance and alignment.I'm having difficulty understanding section 6 and 7, second and third IF alignment, it does not make sense to me..for example it says set sig gen to 2.9 mhz and display should read 100 khz?, don't understand thisthe instructions seem to be very not detailedHave you done the IF alignment as described in the manual?

author: xrunner
author_rank: Super Contributor
timestamp: September 18, 2021, 07:13:27 pm
content: Quote from: radiojack on September 18, 2021, 06:01:46 pmYes I've done it. You are attaching the sig gen set to 2.9 or 2.1 MHz to the IF section - not going into the external antenna connection, for example for the 2nd IF you attach to TP 105 and TP 106 (GND) and the 3rd IF to TP 401 and TP 406 (GND). The MHz setting of the radio has no effect here. You simply tune the kHz dial of the radio to wherever it states, i.e. 100 kHz or 900 kHz. Follow the instructions just like it states.

author: stevepullan
author_rank: Newbie
timestamp: December 12, 2021, 11:49:34 am
content: Thank you xrunner for a very detailed and informative series of posts.I have just acquired an FRG-7000 which is totally deaf and the information you present here will be valuable for me as I travel down that same path.Cheers.

author: xrunner
author_rank: Super Contributor
timestamp: December 12, 2021, 12:06:54 pm
content: Quote from: stevepullan on December 12, 2021, 11:49:34 amThanks. Please use this thread (if you choose) to post any progress you would like to share.

author: LA3DNA
author_rank: Newbie
timestamp: October 09, 2024, 05:42:51 pm
content: Thank you "radiojack" to post your restoration project to the FRG-7000.I have an similar model here that need some care, it's working but I like to replace all the capacitors and replace the front bulbs with LED-lights.I'm gone do a full alignment to the receiver, I'm quit new to electronic but have been a HAM-operator for many years so I know the basic.Now my question; Do I need to use an Vacuum Tube Volt Meter (VTVM) like described in the "Alignment Procedure" or can an normal modern Multimeter be used? (or alternativ analogic volt meter)Leif / LA3DNA

author: xrunner
author_rank: Super Contributor
timestamp: October 10, 2024, 12:39:12 am
content: Quote from: LA3DNA on October 09, 2024, 05:42:51 pmOh by all means use a modern DMM.

author: Dave Wise
author_rank: Regular Contributor
timestamp: October 11, 2024, 04:50:36 pm
content: Many VTVMs put the last 1M of input divider resistance at the probe tip. I don't know of any DMMs that do this. If you probe a sensitive node the DMM may perturb circuit operation. Add some resistive isolation at your probe tip, and do the math to correct the reading.