I think someone changed or limited the amount of power to my Sceptre

[Lokibleed]

I bought this amp with the intend of changing a bad power transformer so, I ordered a hammond 374bx 375-0-375 to replace the old one. No big deal right, well I just opened up the chassis and things just don't look right to me. Let me say I'm no Amp expert by any means but, I know I'm capable of doing a recapping. With that being said I've checked out schematics here. think someone has added a crap load of resistors to reduce or limit the amount of voltage going through the cicuit.
Here's a list of electrolytic cap left in the chassis
Mallory 30uf 500v(metal)
50uf 150v(paper)
50uf 150v(paper)
50uf 50v(paper) w/resistor attached to it.

By the looks of the schematic I'm missing some caps. haven't made out all the resistor values yet. I think a feel a head ache coming on.
I'll post some pictures of it soon if anyone is interested.
Any suggestions would be very cool. the chassis tells me its a 68' sceptre.
I just want her to sound like she was built to sound like.

[loudthud]

What made you get the 374BX? Sunn sometimes used two resistors in parallel in the decoupling string when correct values were not available. The 50uF@150V sound correct for the bias supply. One near the standby switch and one between one of the long power amp terminal strips and the tremolo board.

[Lokibleed]

The reason I got the 374bx was because of this review on Harmony-central
 http://reviews.harmony-central.com/reviews/Guitar+Amp/product/Sunn/100S+Head/10/1
50vac bias tap
correct filiments

[Lokibleed]

Doesn't it seem like I'm missing some power caps.

[loudthud]

The big can cap should be a 30-20-20-20@525V. Yours may have been replaced. I used one of these transformers in a 200S and it fit perfectly.

http://store.triodestore.com/mq782.html

[Lokibleed]

Hey Thud, Your right its the big can thats missing check it out.

[loudthud]

The part identified in the picture below is your main filter cap. I can't tell from the camera angle but it should have four terminals in the center part and four twist tabs that extend through slots in the little plate that is riveted to the chassis.

[Lokibleed]

Thanks Thud.

[Lokibleed]

So the absence of the big can is do to the solid state diode rectifier. I think I get it.  Thanks again.

[basiklybass]

I would seriously consider replacing the 4 cap can if it has not already been replaced. These cans leak and get weak after 20 plus years and the main effect is a blown power transformer. It would be a shame to replace the PT and then have it fail again because of bad power caps.

Someone is selling these cans again or you can put individual components in. Search for threads, especially ones that SoundmasterG has responded to. Somewhere a few years ago he posted a great step by step instruction on upgrading your power section on these amps.

[Lokibleed]

These are photos of the new transformer hammond 374bx.




 I have not powered it up yet. I think I am going to change the caps first.

Any suggestions to what else I should change would be great

[mckinnon audio]

  Hi there,not to be a picky old fart,(but I am),I'd recommend you twist your heater line wires,both the 5 volt and the 6.3 volt windings,will make things a little quieter,good luck,Mel.

[Lokibleed]

  Hi there,not to be a picky old fart,(but I am),I'd recommend you twist your heater line wires,both the 5 volt and the 6.3 volt windings,will make things a little quieter,good luck,Mel.

First off, thanks for taking time to look/respond at this thread. I could use any advice no matter how small it is. I really appriaciate everyone who has taken the time to respond to my posts because I know some of these posts are sound retarded..

 I am just beginning to understand tube amps and probably shouldn't be working on them but, for me its the only way to learn.
 I found that tube amps(old tube amps) are by far much better sounding than most crap companies put out today and futher more I would like to understand more about the circuitry behind it. As of now I am just trying to ressurect this part of art to her glory.

Please be patient with me and thank you

[mckinnon audio]

  Hey Lokibleed,just trying to help out another Sunn amp maniac,good luck,Mel.