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Old 30th October 2010, 02:13 AM   #1
chops is offline chops  United States
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Question Project: Baldwin Tube Amp...

I haven't been here for a while, but when I was, I was usually in the loudspeaker sections. Anyway...

I have an old Baldwin organ amp which dates back to the mid 50's. It was converted over to stereo operation by Will Vincent a couple years back on the cheap as some kind of deal between him and a mutual friend of my brother's. Well since it was a quick and dirty conversion, none of the original caps were replaced.

A few months down the road, my brother was listening to his system (I was there too), the amp started making very loud ticking and popping sounds through the speakers, so much so the speaker drivers were jumping violently and it scared the pooh out of us! We seriously thought that the speakers might have gotten damaged, but luckily they didn't. However, when it was working, it sounded darn good as I had tried it out on my system for a few days before hooking it up to my brother's system. It blew away the Adcom GFA-555 Mk II amp I had at the time in every way possible.

To make a long story short, I'm planning on recapping this amp to use in my system on my NHT 2.9 loudspeakers. They're rated at 86dB @ 1w/1m and the amp is rated somewhere between 23-28 watts per channel with its P-P 6L6's. The driver tubes are NOS RCA 5751's and it uses not one, but TWO 5U4's. The good thing about using this amp with these speakers is that I now live in an apartment and the speakers never see anymore than about 2-3 watts max, so this old Baldwin amp will be more than enough power.

As for caps, I've got a list...

PS & Filter caps (old 3-section aluminum cans)
(2) 50uF - 100v+
(4) 40-50uF - 450v+

Coupler Caps
(4) 0.1uF - 600v+

Bypass Caps
(2) 100pF - 600v+


When I get some time, I'm going to check all the resistors.


I've found some Xicon 47uF-450v at PE that I think I can use to replace the old 3-section can caps (PS & filter). For the coupling caps, I found the Audiocap PPT Theta caps which get great reviews and are about the most I want to spend. As for the bypass caps, my father has some new 120pF - 400-500v Mica caps that I can use. He said the original Mica bypass caps are most likely good, but I'd rather change them out anyway.

So I was just wondering if you guys had any suggestions or anything for me and this amp. I'm all ears!

Many thanks in advance!

As always, here's a few pics of the amp in its current state...

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.


BTW, all of the tubes tested perfect. I was told the 6L6's are brand new and only used for a couple months.

Click the image to open in full size.

Last edited by chops; 30th October 2010 at 02:18 AM.
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Old 30th October 2010, 02:29 AM   #2
taj is offline taj
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I'd love to see a schematic of this amp. Do you plan on tracing it out?

..Todd
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Old 30th October 2010, 02:39 AM   #3
chops is offline chops  United States
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If I knew how, I would.
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Old 30th October 2010, 03:52 AM   #4
taj is offline taj
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Well, if you can take a couple of clear photos like the second one above, but zoomed in 2-3 times so I can see exactly where everything is connected, I can draw a schematic. you may need to answer a couple questions along the way.

..Todd
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Old 30th October 2010, 03:56 AM   #5
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good to see you here chops!
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Old 30th October 2010, 04:09 AM   #6
chops is offline chops  United States
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Quote:
Originally Posted by taj View Post
Well, if you can take a couple of clear photos like the second one above, but zoomed in 2-3 times so I can see exactly where everything is connected, I can draw a schematic. you may need to answer a couple questions along the way.

..Todd
I can certainly do that Todd. I'll take the pics tomorrow morning but will only be able to post in the evening.


Quote:
Originally Posted by aardvarkash10 View Post
good to see you here chops!
Likewise aardvark! Small world, huh?
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Old 30th October 2010, 04:55 AM   #7
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Default Hey Todd,

Quote:
Originally Posted by taj View Post
I'd love to see a schematic of this amp.
With only one 5751 as a driver per channel, it won't be anything terribly exotic. Probably a concertina with cathode bias finals.

jeff
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Old 30th October 2010, 05:21 AM   #8
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Concertina is a nice splitter, by the way. Terribly exotic does not necessary mean very good.

Also, that green paper caps may be still very good. I have some Tiny Chief caps of similar design, they are still perfect (made in 1960'th)
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Old 30th October 2010, 08:04 AM   #9
teemuk is offline teemuk  Finland
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This is a typical Baldwin design:
Click the image to open in full size.
The scan is poor but you get the overall idea.
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Old 30th October 2010, 08:11 AM   #10
taj is offline taj
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Hey VinylKid, yeah that's why I was curious.

Yeah, Teemuk, that must be it. Or something AWFULLY close. (Saved me from drawing it).

Wave, you mean these? I've got some too. The photo doesn't do justice to their 'pinkness'.


..Todd
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Last edited by taj; 30th October 2010 at 08:25 AM.
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