Author Topic: My first tube AMP... HELP !  (Read 6070 times)

Offline darrylo

My first tube AMP... HELP !
« on: February 20, 2009, 09:35:04 AM »
I picked up a dusty old Pioneer SX-34b from a friend for nothing.  :)

Unfortunately the 6AQ8 tube on the FM tuner is cracked and broken.
The output valves are working but are mismatched brands.
I've also read that I should replace most of the Caps before doing anything else.

Does anyone know a local source for these valves and caps ?

Good news is it still works and sounds ok.

I'm looking at hooking them up to a ancient pair of Pioneer speakes that have been in my garrage the last 10 years.... After I repair the tweeters, rebuild the boxes and the crossovers.

later.
Always Looking for Heathkit, AVO and Leak
"I refuse to prove that my cables will make your system sound better", says the snake oil vendor, "for proof denies faith, and without faith, you will hear nothing."

Offline Family_Dog

Re: My first tube AMP... HELP !
« Reply #1 on: February 20, 2009, 11:00:43 PM »
Hi Darrylo,

Lekker!


An ECC85 is as close as dammit to the 6AQ8 and may be easier to find. The ECC85 is listed by Mr. Valve (bouwman (at) telkomsa.net) at prices from R115 to R170.

I don't know where you are situated, but yes, you do need to replace the coupling caps and I find the older Pioneer radios normally have dud caps on their loudness circuit, which kills a channel. Shops such as Mantech, Communica & RS Components should be able to assist you with the caps, coupling and Filter electrolytics. Mr. Valve does stock various filter caps as well.

Please place a photo of your Pioneer here, enquiring minds need to be able to look (and drool!  ;D ) over it.


-F_D



-Eric

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

Offline ghostinthemachine

Re: My first tube AMP... HELP !
« Reply #2 on: February 22, 2009, 05:43:35 PM »
Very nice!

I will second FD's request for a pic - please!  ;D
Conquer yourself rather than the world - Rene Descartes

Offline darrylo

Re: My first tube AMP... HELP !
« Reply #3 on: February 23, 2009, 07:32:57 AM »
No problem... I'm just far from a PC until later this week but I'll post them ASAP.

Think is I'm not sure where the coupling caps are.... so I'll needthe help.


Regards
Always Looking for Heathkit, AVO and Leak
"I refuse to prove that my cables will make your system sound better", says the snake oil vendor, "for proof denies faith, and without faith, you will hear nothing."

Offline darrylo

Re: My first tube AMP... HELP !
« Reply #4 on: February 27, 2009, 01:18:26 PM »
As promised here is the pics.
Always Looking for Heathkit, AVO and Leak
"I refuse to prove that my cables will make your system sound better", says the snake oil vendor, "for proof denies faith, and without faith, you will hear nothing."

Offline Family_Dog

Re: My first tube AMP... HELP !
« Reply #5 on: February 27, 2009, 08:03:55 PM »
Darryl, that set is worth restoring. As I mentioned, ECC85 valves are available in JHB. You should replace the coupling caps as well, these are only a few cents each but you do need suitably rated high-voltage ones. These are available from Mantech, and probably places like RS Spares, Communica and Yebo. The electrolytic caps (the large ones on top of the chassis) might require replacement as well, or you can try reform them. You do this with (preferably) a Variac inline with the AC supply and slowly stepping up the AC mains voltage over a few hours, or by means of a 100w 220v globe wired in series with the one of the AC mains leads (Note: In "Series" - i.e. in one wire only, not in "parallel" across both wires).

Where do you live? What type output valves does the amplifier use? I've been trying to source a schematic for the receiver, but no joy. Not the end of the world, it's useful, but not really necessary.


-F_D





-Eric

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

Offline darrylo

Re: My first tube AMP... HELP !
« Reply #6 on: March 02, 2009, 07:56:10 AM »
I did manage to find this site that has some scanned diagrams.

http://www.htg2.net/index.php?topic=41338.0

I'm in Alberton Jhb.
Always Looking for Heathkit, AVO and Leak
"I refuse to prove that my cables will make your system sound better", says the snake oil vendor, "for proof denies faith, and without faith, you will hear nothing."

Offline Family_Dog

Re: My first tube AMP... HELP !
« Reply #7 on: March 02, 2009, 07:25:00 PM »
Interesting site that, I'm at a loss for words but the guy did a neat restoration job! His photos are helpful too.


-F_D



-Eric

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