Sanyo RP-8880 repair?

[godzilla]

Hi everyone. NewB here.

I have a Sanyo RP-8880 SW receiver that is dead on all the SW bands SW-1 through SW-5. It does seems to receive AM (MW), MB, LW fine. FM works too but tuning meter does not deflect (weak signal).

I bought this quite some time back and was told that this is a common problem with this model, and that the fix is a blown FET in the front end. Well, turns out that the "fix" might not be that easy after all -- I replaced 4 of the 6 FET's including one expensive metal canned J-FET with absolutely no change. The remaining two are completely submerged beneath wax so I was hoping to do those as a last resort. Those 2 remaining FET does not look like they would be where the issue would be. I have heard at least one other owner did the exact same thing -- replaced all the transistors and the caps with no improvement. :sad:

I DO see that this is a common problem because searches indicate that many of these being offered for sale have this exact same issue.

Does anyone else have this model and familiar with this issue. Hope someone here can help. I really like this little radio. HELP ME, HELP ME, HELP ME PLEASE!

Norm.

It looks like this one:

 

[godzilla]

Wow. NOBODY has one of these guys?

 

[BG46]

sanyo

I have the same unit, the only thing on mine that works is the FM band. Would sure like 2 get it fixed, it,s a nice radio

 

[godzilla]

Well, that's what I'm saying. This is such a common problem with this model that someone out there MUST have fixed this. Just looking to see if someone can share how they did it and which components they ended up replacing to restore those bands.

 

[Shortwavenut]

hngfxngf

 

[godzilla]

OK. I will give it a try. Someone else said to replace the FET's and like you, I replaced all the 2SK49's and the very expensive 3SK59 JFET to no effect.

It is a pain to disassemble, no doubt but can be done. The trick is to secure the huge dial wheels with screws before disassembling.

I have (2) of these Sanyos and both have the same problem with non-existent SW. On one, the FM is working but the LW/MW etc is a bit weak. On the other, FM is very weak and everything else is dead as a doornail.

 

[Shortwavenut]

bvfdszhyzdet

 

[godzilla]

OK. I will check it. I don't think I can get to it for a week or so though. I got my hands full at the moment with another project. Yes, I have already cleaned all the contacts ad nauseum and I used deoxit D5, which is probably a better product than the RS stuff -- and I'm convinced that is not the problem. The 2SC930's should be listed in the service manual. I have a bunch of 2SC930's and they were sold to me by a guy in Canada but they look smaller than the original Sanyo transistors so they might be chinese knockoffs. :sad: My experience with chinese knockoffs is not good.

On one, the weak FM means you have to turn volume all the way up to hear it but the RF strength is weak too. Not even a blip on the SW or MW/LW bands though.

BTW, do you have a good readable service manual or is it the downloadable one that is floating around the web? I am looking for a better copy.

 

[Gregory]

Just repaired my Sanyo RP8880

I have a Sanyo RP8880 radio that only works on FM MW LW MB only and not on the SW bands. Anyway I hear this is a common fault with these radios. After around 5 attempts I finally fixed my radio. To get the best out of the short-wave band add an external antenna.

I managed to repair my radio and get the SW fully working after trying to fault-find without a signal generator or frequency counter. To get to the circuit board you will have to secure all tuning dial drums to the plastic chassis. There is a small hole in the drums that can be locked in place with a small screw. Then unclip the main circuit board carefully pull away from frame. Now you should be able to work on the circuit board with ease.

Also the front-end R.F. peaking control can be very tricky to tune, it’s the one that moves a ferrite rod in and out of a coil for peaking the SW RF input. Be careful you don’t have a broken coil wire, this will also cause a dead set on all the short-wave bands too. While you have the board open and with a circuit diagram next to you, it’s a good idea to check with a multi-meter all the switch connections just to make sure your problem’s not to do with any bad contacts.

I build receivers for a hobby so this radio was a challenge to repair use 2N2222A transistors for the oscillators they work fine and are cheap instead of 2SC930D. Also 2N3819 FET's will do fine too and for the dual gate MOSFET use 3N201 or BF981, BF961, 3SK88. BF981 cheap at 0.70 pence bit fiddly to fit haven't tried it on this radio, used them for my home brew and works ok with ferrite beads on MOSFET leads to stop VHF parasitic noise.

First download circuit diagram from http://www.dr-boesch.ch/radio/radio-manuals/sanyo-rp8880-service-manual.pdf

1. Q108 SW oscillator transistor 2SC930D measured ok but no output I replaced it with 2N2222A got this section working.
2. Next fault was the front end Q106 F.E.T replaced with 2N3819 or quick test by swapping over Q101 and soldering it in place of Q106 if your FM is working fine your SW front end will be ok too once you swap F.E.T around. Got this section working too.
3. SW 2nd oscillator 2SC930D that’s Q111 replaced with 2N2222A got this section working.
4. If nothing happens replace mixer MOSFET too a 40673 will do, mine was ok.

 

[ruudyl]

Sanyo rp 8880 FM

Hi Gregory

I have 1 of these radio', actually 3, all have problems.

One is working quite wel just missing half of the FM band, what do you think could be the problem, and what parts must I replace

Hope you can help me

Friendly greetings Ruudy

 

[mechanic]

In a receiver this old there may be issues with the electrolytic capacitors, especially with the DC to DC converter as it is a battery radio. This could throw the voltages off in PLLS or oscillators causing them to be off on frequency coverage. Check the VCO electrolytics and the voltage supply capacitors.
Check for poor or cold solder joints as the flow method used at this time was not very good and components that would "sink" heat more were likely to be incomplete in soldering. Sometimes containments could prevent solder from making a good connection, :sneaky2:
With the FET problems and low receive you may want to look at the two diodes just after the antenna input. Usually they are signal, glass type and are used to shunt any static or signal spikes to prevent damage to the front end amplifiers.
From what I can see the Sanyo is similar to the Panasonics and they are from a similar time line of production.

73 Rod aka mechanic

 

[Gregory]

Hi Ruudy,
sorry for taking a long time to answer you I just logged on after 3 months and saw your reply. change Q103 this is the oscillator transistor. You may have a fault some where else in the circuit but its difficult to offer much advice without me working on the radio to trace the fault. Give it a try my oscillator transistors where bad these usally go faulty.

Your missing half the FM band then you oscillator transistor could be ok maybe someones played around with the trimmer capacitors for the FM band tracking VC1-1 VC1-2 VC1-3 download circuit diagram from http://www.dr-boesch.ch/radio/radio-...ice-manual.pdf to view trimmer capacitors. You may need to adjust them to get the correct band tracking, mark them with a felt tip pen so you can go back to the orignal positions.

From Gregory

 

[Ronaldo]

Eu comprei este modelo de rádio pouco com o mesmo problema: Você não recebe FM e SW; Alguém encontrou o componente responsável pelo problema. Obrigado

Hi Ruudy,
sorry for taking a long time to answer you I just logged on after 3 months and saw your reply. change Q103 this is the oscillator transistor. You may have a fault some where else in the circuit but its difficult to offer much advice without me working on the radio to trace the fault. Give it a try my oscillator transistors where bad these usally go faulty.

Your missing half the FM band then you oscillator transistor could be ok maybe someones played around with the trimmer capacitors for the FM band tracking VC1-1 VC1-2 VC1-3 download circuit diagram from http://www.dr-boesch.ch/radio/radio-...ice-manual.pdf to view trimmer capacitors. You may need to adjust them to get the correct band tracking, mark them with a felt tip pen so you can go back to the orignal positions.

From Gregory

I bought this little radio model with the same problem: You do not receive FM and SW ; Someone found the component responsible for the problem. Thank you

 

[Derundurel]

My father bought one of these in about 1980 and used it frequently for some years. Sadly, it has spent quite a few years "resting" in my loft before I got around to blowing the dust off it. It was initially completely dead, but started coming to life after cleaning the switches carefully. The FM band was dead until the VHF local oscillator transistor (Q103) was changed. This necessitated realignment of the local oscillator. MW, LW and FM all work very well now but SW is extremely weak. The relevant local oscillator is running but given the comments above I suspect one of the FETs, e.g. Q106.

 

[Derundurel]

Over a year later, I've finally got around to looking at this again. It had me stumped for ages, as every stage in the SW section seemed to work, but it took about 50 mV of input signal to get any audio! The biggest breakthrough was the discovery that the ceramic resonators had drifted. The 2nd IF centre frequency is now 472 kHz, which is quite a way away from 460 or even 455 kHz (both figures are quoted in the manual!). Re-aligning for this new IF brought the set to life. The 1st IF resonators had drifted too, to about 10.77 MHz. One solution would be to replace these, but I found it easier to re-align the set. I have a spreadsheet that was useful for this should anyone be interested. There is still some alignment work to do for some of the SW bands, but the set essentially works at last.

I have also tided up the manual quite a bit. I'll upload it if anyone is interested.