Author Topic: Pioneer SX-34Bs advice  (Read 1804 times)

Offline MusicMan_ZA

Pioneer SX-34Bs advice
« on: July 16, 2014, 07:49:17 PM »
I was lucky enough to pick up my first-ever valve amp, in the form of a Pioneer SX-34Bs Receiver, today, for a reasonable price. It is in good working condition, and all 13 valves seem to work (they light up - but what do I know?). It has phono input (magnet), phono input (ceramic) (which is also the auxiliary, one "high" and one "low"), tape input and tape output.

The tuner works fine, the auxiliary works fine (playing my external USB DAC through it sounds amazing, in stereo!) but there seems to be a problem with the (magnet) phono input - the Right channel works perfectly, but the Left channels is "dead". The funny thing is that the RCA connector on the amp for the Right (working) channel is loose (wiggly) and the RCA for the Left (dead) channel is firm (normal). When I change the turntable RCA leads around, the Left one works fine in the amp right channel, and the Right one does not work in the amp Left channel. So if would seem that it is a problem on the amp side, but only for the (magnet) phono input!?

Any advice as to what I should do next?

Some picture:











Thanks in advance,
Johan
I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline prajayn

Re: Pioneer SX-34Bs advice
« Reply #1 on: July 16, 2014, 08:12:15 PM »
Very nice.

Offline Family_Dog

Re: Pioneer SX-34Bs advice
« Reply #2 on: July 16, 2014, 09:28:05 PM »
Quote
Any advice as to what I should do next?

Well.... you could send it my way but I guess that is not the reply you are looking for.   :drool:

First, look for the service manual on the 'net, it should be available. Then follow the input from the phono stage to the valve, possibly something wrong with the RCA socket. With the volume set to about 15-20%, if you touch the input ("live") of the RCA socket with a piece of bare wire or similar you should hear a hum from the speakers. If not, try jiggling the stereo/mono switch as well as the phono select switch - the contacts might have gone high-resistance as a result of becoming tarnished.

You can also check the valve bases for the same reason and even try swapping over V1 & V2, these should both be 12AX7 (ECC83).

Let's start off with just this.


-F_D





-Eric

That Guy in South Africa...
*************************************
http://groups.yahoo.com/group/vintage_tube/
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Offline MusicMan_ZA

Re: Pioneer SX-34Bs advice
« Reply #3 on: July 16, 2014, 09:37:02 PM »
Thanks, FD - I will try all this, and report back. Here's holding thumbs!
J

I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline scrarfussi

Re: Pioneer SX-34Bs advice
« Reply #4 on: July 16, 2014, 09:37:30 PM »
lets see underneath
suum cuique pulchrum est


"Then Said my heart here will i take my rest."

Offline Skylark

Re: Pioneer SX-34Bs advice
« Reply #5 on: July 16, 2014, 09:46:30 PM »
Very nice, looks in smart cond considering its age
Music is in the Mind

Offline Moolz

Re: Pioneer SX-34Bs advice
« Reply #6 on: July 16, 2014, 10:24:57 PM »

lets see underneath

+1!
Beautiful looking amp.

Offline MusicMan_ZA

Re: Pioneer SX-34Bs advice
« Reply #7 on: July 17, 2014, 08:06:07 PM »
Ok, so far:

Quote
With the volume set to about 15-20%, if you touch the input ("live") of the RCA socket with a piece of bare wire or similar you should hear a hum from the speakers.

When I do this, there is a hum from the working channel, and nothing from the "dead" channel.

Quote
If not, try jiggling the stereo/mono switch as well as the phono select switch - the contacts might have gone high-resistance as a result of becoming tarnished.

Made no difference. Should I spray with Servisol contact cleaner, and wiggle some more?

Quote
You can also check the valve bases for the same reason and even try swapping over V1 & V2, these should both be 12AX7 (ECC83).

I would like to try this, but which valves are V1 and V2?

Yes, I am clueless regarding this!  :facepalm:
Thanks,
Johan
I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline Family_Dog

Re: Pioneer SX-34Bs advice
« Reply #8 on: July 18, 2014, 07:26:32 AM »
I don't have the layout of the amp but very often the chassis of the receiver is stamped with the valve type. Being Jap, it should be stamped 12AX7. These valves are very hardy and rarely give trouble, but they are some 40+ years old. Most likely the two valves that are screened with metal cans in your pic above. But you could also swap the four big valves around (6BM8) that are in the top right of your amp. Maybe one of them has gone bad. If still no joy, time for fault-finding below the chassis.

Can you paste a decent under-chassis pic?


-F_D



-Eric

That Guy in South Africa...
*************************************
http://groups.yahoo.com/group/vintage_tube/
*************************************

Offline sav

Re: Pioneer SX-34Bs advice
« Reply #9 on: February 11, 2020, 07:45:03 AM »
@MusicMan_ZA Did you ever get your amp sorted?


Offline MusicMan_ZA

Re: Pioneer SX-34Bs advice
« Reply #10 on: February 11, 2020, 06:44:29 PM »
@MusicMan_ZA Did you ever get your amp sorted?

No, I did not.
But I sold it to someone - as is - and from what I understood, he fixed it.
Not sure how, or what they did - the technician was from the Congo and lived in Dunoon in Cape Town!

I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline sav

Re: Pioneer SX-34Bs advice
« Reply #11 on: February 11, 2020, 07:04:53 PM »
No, I did not.
But I sold it to someone - as is - and from what I understood, he fixed it.
Not sure how, or what they did - the technician was from the Congo and lived in Dunoon in Cape Town!
Wow, cool! Looks like it's getting more and more difficult finding reputable people to work on these things.
I've also got one which has started acting up.

Offline Qualityten

Re: Pioneer SX-34Bs advice
« Reply #12 on: February 16, 2020, 01:31:38 AM »
Start a new thread in the valves forum, and try and describe the problem carefully. Pics help. Say when it was last working correctly. We may be able to resolve the problem there.  And those 6BM8 valves sound good. 

Having said that my Pioneer receiver required a lot of work.

Offline marantz123

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Re: Pioneer SX-34Bs advice
« Reply #13 on: February 16, 2020, 10:16:11 AM »
If the good advice steps in this thread have been followed thus far, try inspecting the selector switch carefully. Pull the covers (the bottom one gives a better view/access in this situation) and rotate the selector to phono and take a good look at where the contacts have settled....you could have a badly oxidized contact or a disconnected left channel phono wire which is "floating" without any contact to anything..(wiggle it gently..to check its firmly connected)..hence this possibility causing the dead phono channel. Had a similar selector issue in an SX410....similar wiring and selector with a disconnected/broken wire at one of the wafer switch contacts.

Another thing I have found is that a good magnifying glass and a bright torch is invaluable when inspecting tight, busy areas like this ..no matter how good the ambient light is.

Edit: I just read after posting this that the amp was sold on and repaired by someone....so this post is not applicable now but will leave it here as part of such fault-finding in future cases, if any.
« Last Edit: February 16, 2020, 10:24:01 AM by marantz123 »

Offline MusicMan_ZA

Re: Pioneer SX-34Bs advice
« Reply #14 on: February 16, 2020, 06:49:08 PM »
[quote author=marantz123 link=topic=35629.msg973664#msg973664 date=1581840971

Edit: I just read after posting this that the amp was sold on and repaired by someone....so this post is not applicable now but will leave it here as part of such fault-finding in future cases, if any.
[/quote]

Thanks, anyway - all advice is always appreciated, and may very well be very useful to other people, or for any/many future projects!  :2thumbs:
I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...