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Old 1st May 2012, 05:27 PM   #21
pancaQe is offline pancaQe  United States
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@ Jim McShane,
You are correct about the IC cap, it definitely is not original, it's 500V, 22uf. The terminal strip to the left has a white wire coming off the bias pot and a cap 25v 220uf to chassis along with a 68K resistor to chassis. Basically I need to know what wires go where and what is missing. I know there's the filter caps (which I believe was a three in one type) and the large chassis mounted resistor is supposed to be 100ohm (don't know wattage). There are two red leads to each OP x-former, one white lead from the primary PS xformer, one red wire from pin8 of the rectifier tube socket. Once I get it running then I can start with the mods on the rectifier. Here's a closer look at the area in question. Thanks for all the help and suggestions. I've already ditched the JJ rectifier for a GE I had lying around.
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Old 4th May 2012, 04:25 AM   #22
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So does anyone have any ideas on how the best way to get this amp up and running. Cap values, resistors etc. From what I can tell it just needs filter caps and any related resistors. Any suggestions would be great. Thanks
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Old 4th May 2012, 05:32 PM   #23
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I suggest you go to tubesandmore dot com and look at their selection of multisection can caps. You will need a maximum 47 or 50 uf section for the first and then perhaps a bit larger after. I think you will want to use 450V rated caps. I have also used the black JJs that are mounted with clamps with good results.

You do need to arrive at a value for the missing resistor and that part is probably unobtanium. You can however buy a modern wire wound chassis mount part like THIS and mount it inside the chassis.

If you can't find a schematic, you might take a few hours and make a circuit drawing and post it here and it's likely you will get sound recommendations for that resistor value.

Last edited by Captn Dave; 4th May 2012 at 05:37 PM.
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Old 4th May 2012, 08:00 PM   #24
pancaQe is offline pancaQe  United States
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Thanks Captn Dave, The missing chassis mounted resistor I believe is 100ohm. The gentleman who gave the amp also gave me 6 or 7 other tube amps in various stages of completion along with many bags of parts some old some NOS some new. He believed that one particular bag contained the parts for this amp. A Sprague electrolytic 40uf-40uf-20uf - 450vdc cap and 100ohm chassis mounted resistor look to be the most likely candidates if that seems plausible according to their values. I'll start a hand drawn schematic, never have attempted that so we'll see how it goes.

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Old 4th May 2012, 11:30 PM   #25
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The cap values sound plausible. A C-EC40X3-525 from antique electronic (tubesandmore.com) would do just fine if you need a three section can. You can go up on voltage but not down. The first cap is limited to 60uf by the rectifier's design limits (rather than 50 as I said in my first post) and the additional sections can generally be increased in value with positive results. You may connect two or more sections if you desire for the additive value.
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Old 4th May 2012, 11:55 PM   #26
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I was wondering, does the GE 5AR4 which is relatively small in size differ from a Mullard GZ34. I was given one of each and am wondering if one is preferable in this amp.
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Old 5th May 2012, 12:36 AM   #27
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No, they have the about same characteristics. You can google their datasheets and compare for yourself. THIS site is handy. The Mullard is very valuable.
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Old 5th May 2012, 05:52 AM   #28
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Yea I acquired a good deal of parts and tube equipment from relative who was an electrical engineer in the US Army in Japan after WWII. A lot of mil spec tubes and NOS tubes. Boxes of PIO caps like Vit Q, Aerovox, Pyramid, Jensen. 4 Bogen pa mixer amps, The Fisher intergrated amp, HH scott, Heathkit, 4 weird Moviola tube amps. I haven't really gone through it all thoroughly but it's a lot of stuff. The Soundcraftsmen is just the first on the list.
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Old 5th May 2012, 06:08 AM   #29
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Me thinks you should consider starting with a more common amp like the Fisher or HH Scott so that you can work from a schematic. Once you cut your teeth on that one you will have enough familiarity to work without a schematic. Just sayin...
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Old 5th May 2012, 07:17 AM   #30
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I think that is a really good idea. I was reading that the Fisher X-100 and the HH Scott 299A that I have are nice sounding amps and schematics are readily available. I think I will be taking your advice Captn Dave. Any suggestions as to which of the two might be a better choice? I'm good at reading schematics and have built one small 6BQ5 single ended stereo amp so I have a little tube experience. thanks
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