1967 Pioneer SX-34, 11W, WORTH FIXING???

[Beaver59]

I got this receiver in pretty poor condition.
Have to say, I'm an amateur and my knowledge is not great at all.
However, plugged this baby in and hooked up some speakers. IT WORKED - AND THE SOUND WAS AMAZING.
I decided to clean the face plate, knobs, dial glass and dust off the inside.
When I turned it back on, the sound didn't seem to be as deep and warm anymore. Don't know what happened.

The bass and treble pots are toast (they were before).
The stereo light comes on during warm up, than goes off and never comes back on again.

I understand and I read, it should be re-capped, but I don't know if I can do this. May be, if someone could lead me and guide me through.
I do have the schematics.

Any advice is appreciated!!!
Scrap it, or fix it.

[TheGimp]

The big issue with working on tube amps is SAFETY. You will be working around potentially lethal voltages and currents.

How much experience do you have with electronics? Can you read a schematic and replace components with confidence, so that the issues are differences between SS and Tube technology?

The amp probably has several problems as you have already seen. (1) Caps, (2) base and treble pots (clean first with Deoxit or similar), (3) possible contaminated tube sockets (clean and retension pin sockets), (4) other age related issues.

Post the schematic please.

Read the Stickies on safety as a good introduction.

[Beaver59]

Thanks Gimp

I wasn't aware of the high voltages, but know now that you say it...., it depends on the current too. The current is the lethal one. Capacitors hold voltages long after an amplifier is unplugged.

It is 35 years ago that I did an apprenticeship in electronics, back in Germany. Not all is forgotten yet, but I didn't practice very much. Yes, I can read a schematic..., a simple one. And yes, I can replace components.
In the SS technology it is the transistor that amplifies the signal. I know this. Tubes do the same thing, different technology though.

Unfortunately, the schematic is 860 KB and the spec sheet is 340 KB, they exceed the forums upload limit and I don't know how to reduce them.
I'll send them to you in an email.

Thanks

[TheGimp]

It appears that you probably have the background bur are rusty.

Looking at what I could find on the web, it looks like that amp should be worth fixing unless something major is bad, like Output Transformers and power transformer.

Hone up your skills and dive in.

Fixing it will take a bit of time as you are on a learning curve.

[Beaver59]

Oh yes, I'd like to dive in and update my know-how.

This receiver has the really cool magic eye 6E5 tube, which is quiet rare.
I love it and look forward to fix it.

I found a couple of links for the spec sheet
AK Database PDF Gallery - Pioneer Receivers/Pioneer SX34 Spec Sheet

and schematic
AK Database PDF Gallery - Pioneer Receivers/Pioneer SX34 Schematic

another spec sheet
Stereo Receiver SX-34 Radio Pioneer Corporat

[Soonerorlater]

Hi Beaver 59,
Came across your schematic a few minutes ago while searching for a Pioneer ER-420 / LX420A. I really like the ECL82 valves the sx-34 uses and coupled with Pioneer output transformers it would be worth the effort to restore.

Or you could strip out the parts and just rebuild the amp section If that's all you need

[Beaver59]

Originally Posted by Soonerorlater

Hi Beaver 59,
Came across your schematic a few minutes ago while searching for a Pioneer ER-420 / LX420A. I really like the ECL82 valves the sx-34 uses and coupled with Pioneer output transformers it would be worth the effort to restore.

Or you could strip out the parts and just rebuild the amp section If that's all you need

Thanks Soonerorlater

Is it from the AK data base?
That is where I got it from, just couldn't upload it, because the file was to large.
This little receiver will be a dandy, when it's fixed

[TheGimp]

The stereo lamp is probably indicating FM stereo signal at acceptable level. It mingt not light unless you are in the FM stereo mode and tuned to a suffiently strong station.

[Beaver59]

Originally Posted by TheGimp

The stereo lamp is probably indicating FM stereo signal at acceptable level. It mingt not light unless you are in the FM stereo mode and tuned to a suffiently strong station.

Yes, I believe so too.
Usually I get 2 local stations in stereo, but not with this receiver.

It gives you the choice of 2 FM settings. 1.) "FM", 2.) "FM mpx"
The reception on "FM mpx" is not as good as the other "FM" setting.
Isn't it, that for stereo reception, one would have to choose the "FM mpx" setting, the straight "FM" setting is for mono reception only.
CORRECT?

However, I haven't seen the stereo light working during any operation, except during warm-up, when turning on receiver.

[Soonerorlater]

Is it from the AK data base

Yep and Yep it will be a dandy, I've read on the net that Tamura made the output transformers for Pioneer, mine are labelled AT6123U and yours are labelled according to the schemo as AT6132, not sure how different they are,