5000X "Unserviceable"? :(

[archibael]

Well, that was disappointing.

Took the 5000X to the shop last week with FM tuner issues hoping the vintage stereo shop that advertised "repairs" could make better progress on it than me. Alas, no. They were able to make the same diagnosis as I was: something in the "FM pack" as it's called in the service manual, but nothing further than that.

I had hoped that as a repair shop they might have tools I didn't, like an FM signal generator so they could further diagnose, but I'm getting the distinct impression their advertisement as a "repair shop" is limited to easy fixes only-- recapping electrolytics or swapping out an output transistor.

I know I'm probably just being bitter, but why did I take it to them just to have my diagnosis (which I told them up front) confirmed? If they knew that part of the FM subsystem wasn't serviceable, why even take on the repair? Likely because they figured I misdiagnosed it, I guess. They probably get a lot of that.

Still frustrating.

They recommended finding a parted-out unit online (they tried and failed) and grabbing the FM subsystem from that, which I already knew was an option. Certainly it's the cheapest and sanest, though I might be waiting awhile to find said parts and they might not work any better than the original ones.

I don't actually believe it's unserviceable: these components are resistors, inductors, transistors, and capacitors. I just don't have the tools to do it, and I recognize that it's probably as complex as f*ck.

Anyone know of a service shop somewhere in the Phoenix area willing and capable of doing hardcore FM work? Or maybe of renting me the right equipment so I can try to puzzle it out for myself?

Thanks for listening to me vent. I'm not sure anyone else would understand.

 

[maxhifi]

1000% agree with you. What are the actual symptoms?

 

[Hyperion]

I'm not sure anyone else would understand.

We certainly do understand, we hear this kind of story all the time.

It is true that some of the electronic parts are not made anymore, so if you have a faulty one (like IF coils for example) the only place to get one from, may be a donor unit - but that's quite rare.

 

[archibael]

It appears from work I did with Morden on this forum 11-odd years ago that it's something in the tuning condensor. Possibly the oscillator off-target. Wasn't able to get much further than that.

I have discovered a parted-out potential replacement in a 5 minute google excursion, which implies the shop I went to didn't actually try all that hard-- they offered to sell me another receiver for $300 though.

Still would rather repair than replace, but at least I have options.

 

[maxhifi]

We certainly do understand, we hear this kind of story all the time.

It is true that some of the electronic parts are not made anymore, so if you have a faulty one (like IF coils for example) the only place to get one from, may be a donor unit - but that's quite rare.

Hah, I like the line from Duck Soup in your signature, that's a great movie.

It appears from work I did with Morden on this forum 11-odd years ago that it's something in the tuning condensor. Possibly the oscillator off-target. Wasn't able to get much further than that.

OK but what's it doing wrong, when you try and use it? Dead FM band? Distorted sound? No stereo? etc.

 

[archibael]

Dead FM band. All other functions are fine. AUX, PHONO, not a problem.

 

[spicer]

Well, that was disappointing.

Took the 5000X to the shop last week with FM tuner issues hoping the vintage stereo shop that advertised "repairs" could make better progress on it than me. Alas, no. They were able to make the same diagnosis as I was: something in the "FM pack" as it's called in the service manual, but nothing further than that.

I had hoped that as a repair shop they might have tools I didn't, like an FM signal generator so they could further diagnose, but I'm getting the distinct impression their advertisement as a "repair shop" is limited to easy fixes only-- recapping electrolytics or swapping out an output transistor.

I know I'm probably just being bitter, but why did I take it to them just to have my diagnosis (which I told them up front) confirmed? If they knew that part of the FM subsystem wasn't serviceable, why even take on the repair? Likely because they figured I misdiagnosed it, I guess. They probably get a lot of that.

Still frustrating.

They recommended finding a parted-out unit online (they tried and failed) and grabbing the FM subsystem from that, which I already knew was an option. Certainly it's the cheapest and sanest, though I might be waiting awhile to find said parts and they might not work any better than the original ones.

I don't actually believe it's unserviceable: these components are resistors, inductors, transistors, and capacitors. I just don't have the tools to do it, and I recognize that it's probably as complex as f*ck.

Anyone know of a service shop somewhere in the Phoenix area willing and capable of doing hardcore FM work? Or maybe of renting me the right equipment so I can try to puzzle it out for myself?

Thanks for listening to me vent. I'm not sure anyone else would understand.

Anything not physically destroyed and not having ICs can be fixed... but FM front ends are a world apart for many audio service people... especially those sealed in soldered together metal enclosures. The area diagnosed is probably correct, easy to confirm with most any tech bench. As was asked, what are the symptoms? Is there any hiss with muting off and volume up... does AM work, a schematic would tell if both use the same IF strip amplifiers. Can't remember which generation but some units from that era used these little round multilegged ICs as amplifiers in the IF strip... looked like transistors except for so many legs... failed all the time... used to replace all of them if one failed. I bet someone on AK will direct you to someone willing and able to service it. Nice set, a great sounding vintage Sansui.

 

[I LIKE MUSIC]

1000% agree with you. What are the actual symptoms?

Yes this and by "FM pack" do you mean the RF front end, which includes the local oscillator and the main tuning capacitor or the the IF signal chain? This is important if you choose to do a board replacement.

Which one did you find on line?

A damaged main tuning capacitor could be an issue, but if the fins and mechanical bits are in tack, even it might be repaired with a little time a patience.

 

[toxcrusadr]

Is PunkerX still doing tuner work up in Michigan? He fixed a couple for me but it's been awhile.

Ah, here we go.

http://www.radioxtuners.com/

"Special rates for AK members"

Be prepared to wait, but he does good work.

 

[kevzep]

Cool story, whatever!!! This tuner is one of the most discrete tuners there is? Sure there are a three 3SK39 dual gate mosfets, but you can get them, I've got, as it happens three sitting in my odd RF components drawer.

I's say there's probably a dead mosfet if the tuner is completely deaf. Their solution wasn't necessary anyway..

There will be someone around that can fix it....I would but I am, of course on the other side of the world so thats no good!!

I hope you find someone...

I love the look on customers faces when they tell me they were told their unit was unserviceable and I tell them, "Nonsense, leave it with me"!!

 

[archibael]

Anything not physically destroyed and not having ICs can be fixed... but FM front ends are a world apart for many audio service people... especially those sealed in soldered together metal enclosures. The area diagnosed is probably correct, easy to confirm with most any tech bench. As was asked, what are the symptoms?

Been so long I don't recall, embarrassingly enough. When I get it back from the shop I'll report back.

 

[maxhifi]

First, I wouldn't take anything that tech said to the bank. The problem could be in the IF strip, or in the tuner front end. A decent tech will be able to narrow this down without a lot of problems... I'd say either find yourself an RF signal generator and an oscilloscope, and start doing some signal tracing, or find a tech who can fix it.

Maybe there's a local ham radio club, or antique radio club, where you could track down a decent tech? This is discrete analog electronics, I don't believe for a moment that it's beyond repair.

 

[archibael]

Yes this and by "FM pack" do you mean the RF front end, which includes the local oscillator and the main tuning capacitor or the the IF signal chain? This is important if you choose to do a board replacement.

Which one did you find on line?

A damaged main tuning capacitor could be an issue, but if the fins and mechanical bits are in tack, even it might be repaired with a little time a patience.

Yes, the "FM pack" is essentially the tuning condensor and associated circuitry like the local oscillator, all RF shielded in the soldered box. I knew going in this was a challenge, I guess I just assumed they'd be up for it.

According to my notes, the IF stage worked okay when fed with a signal from another tuner.

I don't think I'm supposed to post vendor info online, but I found a source for the whole sealed assembly, including tuning wheel-- which part doesn't sound like fun, but I'll roll with it if I have to.

 

[kevzep]

Yes, the "FM pack" is essentially the tuning condensor and associated circuitry like the local oscillator, all RF shielded in the soldered box. I knew going in this was a challenge, I guess I just assumed they'd be up for it.

According to my notes, the IF stage worked okay when fed with a signal from another tuner.

I don't think I'm supposed to post vendor info online, but I found a source for the whole sealed assembly, including tuning wheel-- which part doesn't sound like fun, but I'll roll with it if I have to.

Yep, almost guarantee it will be a dead dual gate FET...

 

[maxhifi]

First you want to make sure the front end is getting power... a shorted C020 would kill power to everything so make sure you get voltage going in. If that's fine, agree with kevzep, either a bad FET, or maybe a bad local oscillator.. local oscillator not running would also kill FM. To make things easy, why not just try replace all three FETs, and also TR101, and see if it magically comes to life. Nothing else in there should really go bad, unless the tuning capacitor is shorted/bent/filthy.

 

[archibael]

First you want to make sure the front end is getting power... a shorted C020 would kill power to everything so make sure you get voltage going in. If that's fine, agree with kevzep, either a bad FET, or maybe a bad local oscillator.. local oscillator not running would also kill FM. To make things easy, why not just try replace all three FETs, and also TR101, and see if it magically comes to life. Nothing else in there should really go bad, unless the tuning capacitor is shorted/bent/filthy.

I'm willing and able, assuming I can find the right replacement parts, I just thought these old analog tuners were persnickety and would need RF gear and an o-scope to align after replacement parts are added or they wouldn't work properly.

 

[toxcrusadr]

The average repair shop isn't going to say 'WE don't know how to fix it, it's kinda beyond our area of expertise' because they don't want you to think they're amateurs. So they say it's unfixable. Would be better if they just said "It's deep in the tuner section and if you want to fix it you have to find a specialized tuner shop. We think it would be too time consuming for US to diagnose and repair." Just like my mechanic tells me I need to go to a transmission shop, and he knows a good one.

 

[maxhifi]

I'm willing and able, assuming I can find the right replacement parts, I just thought these old analog tuners were persnickety and would need RF gear and an o-scope to align after replacement parts are added or they wouldn't work properly.

Well yes, and no. First of all, the really critical alignment is the IF strip, and especially the ratio detector, and the stereo multiplex decoder. Definitely don't start turning screws in the IF cans or you will really mess things up. Also, don't touch/change/breathe too heavy on coils, or adjust the trimmer capacitors without knowing what you're doing. And most certainly don't change any capacitors except for power supply filters. If you just substitute the four semiconductors in the tuner though, it should not really affect the alignment. And if you do knock the oscillator off a bit, all it will do is slightly mess up the accuracy of the dial scale. You really can't make it worse than dead.

 

[archibael]

The average repair shop isn't going to say 'WE don't know how to fix it, it's kinda beyond our area of expertise' because they don't want you to think they're amateurs. So they say it's unfixable. Would be better if they just said "It's deep in the tuner section and if you want to fix it you have to find a specialized tuner shop. We think it would be too time consuming for US to diagnose and repair." Just like my mechanic tells me I need to go to a transmission shop, and he knows a good one.

I would have entirely respected them if they'd have said this. I guess that's part of my frustration.

 

[archibael]

Well yes, and no. First of all, the really critical alignment is the IF strip, and especially the ratio detector, and the stereo multiplex decoder. Definitely don't start turning screws in the IF cans or you will really mess things up. Also, don't touch/change/breathe too heavy on coils, or adjust the trimmer capacitors without knowing what you're doing. And most certainly don't change any capacitors except for power supply filters. If you just substitute the four semiconductors in the tuner though, it should not really affect the alignment. And if you do knock the oscillator off a bit, all it will do is slightly mess up the accuracy of the dial scale. You really can't make it worse than dead.

I'll give it another shot, then. As you pointed out, I can't really break it more.