rogonzab
324 posts
Jul 03, 2013
6:38 AM
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Hi,
I just bought a Teisco 88 tube amp from a local guy. Is a 2x8 and it uses this tubes: 2 12AX7's, 2 6AQ5's, 6AV6 (recitfier?).
I cant find info on the internet, just these 2 websites:
Whttp://organ69.net/ap011.shtml
http://thebakeliteradio.com/page152/page152.html
Does any of you know anything about this amp?
I dont have the amp yet, on fridays I will meet the guy and test/buy this amp.
Thxs!
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HawkeyeKane
1847 posts
Jul 03, 2013
7:07 AM
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I've not come across that particular model before, but I have seen some Teisco tube amps out there. I've heard guitar through them and they sounded pretty good to my ears.
6AV6's are mini 7-pin base preamp tubes. They amount to about one half of a 12AX7. That's puzzling as to why it'd be in an amp that already has a pair of AX7's. Only thing I can think of is that it'd be either your reverb driver or tremolo oscillator. Maybe a phase inverter.
Your mini 7-pin 6AQ5 power tubes are reputed to be virtually identical to 6V6's. I can kinda vouch for that. Buddy of mine has a silverface Musicmaster Bass Amp that uses them, and it sounds pretty darn good for harp.
Just looking at a picture of the chassis on one of the links you posted, the rectifier would appear to be a 6CA4.
All in all, I think you've found a pretty well built amp. Let us know how it works for you!
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Hawkeye Kane
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ReedSqueal
454 posts
Jul 03, 2013
7:08 AM
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Here's a bit more info:
Teisco 88 Amp Info
Info/history on the Teisco name - mainly guitar but amps mentioned
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Go ahead and play the blues if it'll make you happy.
-Dan Castellaneta
Last Edited by ReedSqueal on Jul 03, 2013 7:14 AM
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rogonzab
329 posts
Jul 03, 2013
11:26 AM
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HawkeyeKane (or everyone), how much watts do you think that the amp is?
maybe 10?
Thxs!!
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HawkeyeKane
1850 posts
Jul 03, 2013
11:33 AM
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Well, one of the sites ReedSqueal posted claims 8 watts. But considering the tube configuration, with 6AQ5's being similar to 6V6's, and coupled with the extra gain to drive the reverb, I'd estimate it between 15 and 18 watts. But the two factors that would really help narrow it down would be knowing how it's biased, and whether it's push-pull or single ended.
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Hawkeye Kane
Last Edited by HawkeyeKane on Jul 03, 2013 11:49 AM
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rogonzab
331 posts
Jul 04, 2013
5:49 AM
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I got the amp!
The amps does not work well.
- The volume pot make noise
- The bass pot does not make any difference on the sound
- Is to quiet, maybe 1w or so (whit the volume on 10 I get a clean sound no distorsion o compression at all)
The reverb is very good, and the tremolo is fun.
The amp has never seen a tech, so I guest that is the problem (is a 1964 amp).
The guy soldme the cheaper because of this, so I guess is still a good buy.
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HawkeyeKane
1854 posts
Jul 05, 2013
7:22 AM
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The volume pot probably just has a good amount of dust contamination in it. Try blasting it out with a can of electronics cleaner, and work the knob back and forth until the noise is gone.
If the bass pot is proving to be a dud, it might either have a loose connection on it, or needs replaced altogether. The caps and resistors on the bass circuit might also need checking.
The lack of output is what would concern me most if it were my amp. Do all of your tubes light up? If so, get them all tested. If not, obviously you should replace any dark ones or ones that have an odd glow to them. A complete re-capping job would probably be a good idea as well. The chassis pictures show that this sucker has got a LOT of big e-caps and resistors in it, along with a small can cap. If it's a '64 and has never been gone through by a tech, then some of those are bound to be leaky. Finally, how does your output transformer look? If it looks warped or burned, then it's probably fried. But just out of curiosity, have you tried playing through all three input jacks? Sometimes oddball amps like that have things set up in an ordered configuration you wouldn't expect, and the gain level on the input jacks would be something to fall along those lines.
These are just a few things that come to mind from what you've described. Get her in to see the doctor. Except for the cap job and possibility of new tubes needed, I wouldn't think the items I've mentioned should run you to too steeply, even in Chile. I'll run this amp model by a guy I know and see if he has a schematic for it.
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Hawkeye Kane
Last Edited by HawkeyeKane on Jul 05, 2013 7:23 AM
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rogonzab
332 posts
Jul 05, 2013
8:07 AM
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HawkeyeKane,
I tried all the inputs, but I dont think that tthey are diferent, but I do think that the third one has a litle more bass.
The first 12ax7 has a small glow, maybe is just a reflection of the other.
The next 2 tubes are blue (¿?!)
The rest seems fine.
Why these tubes are blue? it is because they are build to play the blues?
I guess no tube will last 50 years.
Last Edited by rogonzab on Jul 05, 2013 8:09 AM
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5F6H
1648 posts
Jul 05, 2013
8:21 AM
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The power tubes may have a little gassy blue glow at idle, but if they are glowing blue/purple strongly, with no signal, then something has probably failed...turn the amp off.
When you actually play though an amp, the blue/purple gas lights up, this is normal.
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HawkeyeKane
1855 posts
Jul 05, 2013
8:28 AM
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@5F6H
Hmmmm....Mark, would you agree that the inputs might be EQ-based rather than gain-based here?
@rogonzab
Yeah, I remember that now. My friend's Musicmaster Bass's 6AQ5's glowed a little blue when she was at rest.
I forgot to ask you whether or not you happened to find anything stapled to the inside of the cab. Schematic? Tube map? Serial number?
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Hawkeye Kane
Last Edited by HawkeyeKane on Jul 05, 2013 8:30 AM
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rogonzab
333 posts
Jul 05, 2013
9:58 AM
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I open up the amp a here are some pictures:
Uploaded with ImageShack.us
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Uploaded with ImageShack.us
Last Edited by rogonzab on Jul 05, 2013 10:01 AM
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HawkeyeKane
1857 posts
Jul 05, 2013
10:37 AM
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Well, that answers one other thought I had about your lacking output. I just read on Wikipedia that Chile is a 220V country, so your voltage should be ample.
I do see some differences between your amp and the link pictures posted beforehand. All that wiring looks relatively new though. Odd.
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Hawkeye Kane
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HawkeyeKane
2118 posts
Oct 24, 2013
4:27 PM
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rogonzab....not sure if you're still interested, or if you even still have the amp, but I received this email tonight.
"Hello HawkeyeKane,
referring to this thread
http://www.modernbluesharmonica.com/board/board_topic/5560960/5437019.htm
maybe you want to pass the schematics of the amp to rogonzab or post them in the thread. They should be attached on the inside of the backpanel, but as you can see on the second picture, on his amp it´s not there.
He has no emailadress in his user profile, and I´m not registered in the forum, so I send it to you..
best regards
Alain"
He attached two schematic images. I'll post the smaller one since the other one is almost 4 MB in size.
If you email me, I'll forward both to you.
hawkeyekane at yahoo dot com
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Hawkeye Kane
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