silvertone 1484 no sound?

[chuckb]

Hey guys, i have a silvertone 1484 which i've been working on. i can't seem to get any sound. I've replaced all tubes,that i had checked and all are good, they all light up. I have 540v on the B+, checked the voltage at the main filter caps starting with the first 100uf/150v which went 130v,130v,240v 350v and the B+ at 540v. Not getting any voltages at all in the preamp section and no voltage readings on the cap can which holds 20uf,10uf and 5uf.I replaced all the filter caps in the power section (except the thre in the cap can) and replaced the two 25uf/25v in the preamp section. Any help would be greatly appreciated. i guess i should replace the cap can caps as well. Can't seem to track down a 5uf,10uf,20uf can though so i'll have to try and lay them out inside the amp somehow,not alot of room in there though.

[The Dude]

It's best to include a schematic when you start a thread.

[The Dude]

Check to see if your choke is open.

[chuckb]

hey dude ,sorry about the schematic, yes i'll check the choke to see if it's open. there are three wires on the secondary of the ot and there is a speaker jack installed. The three wires are yellow ,redwith yellow stripe and a black. the yellow is going to pin8 of the power tube and the red/yellow is going to the pos of speaker jack , black is to ground,is this correct?

[The Dude]

No OT secondary wires should go to a tube plate. If they did, you'd have B+ on the speaker, or if speaker negative was at chassis ground, you'd be blowing fuses and/or speakers. Are you sure you have that right? I don't know the OT wire colors off hand. You'd have to use a meter to figure out which is which, unless someone else here is familiar with the wire colors.

[chuckb]

hey dude, yes the choke was open, changed it out for another and i have sound although it's low.

[The Dude]

If the choke was open, it's likely something was drawing some extra current to make it open. First suspect would be tubes. I would try swapping in known good tubes and see if you can get the output where it should be. You should also measure plate voltages on preamp tubes now that you have the choke replaced. You might have a plate resistor that's gone towards open.

[g1]

Pin 8 of the power tubes is ground. If you have one of the OT secondary wires (black) going to ground, and yellow also going to ground (pin 8 of power tubes), that does not sound right.
Did you do what The Dude suggested in post #5 and check the ot secondary wires with ohm meter?

[The Dude]

Oh dear!!! I swear that said pin 3. I must need a cocktail.
Apologies.

[chuckb]

yes, the secondary wire going to pin 8 looked suspect to me as well. it was that way when i received it. i removed that yellow wire from pin 8 and checked it with my ohm meter and get 5 ohms, the same 5 ohm reading on the the red/yellow wire. i tried the amp with the yellow not connected and got loads of volume now. so both red/yellow wire and the yellow wire are two 4ohm taps?

[The Dude]

Reading this thread, I think the yellow is 4 ohms and the red or red/yellow is 2.6 ohms.

[chuckb]

yes, that sounds correct dude. i soldered the yellow on the speaker jack and heat shrinked the yellow/red wire. Amp works good now. to bad i replaced all the filter caps but it's done now. i replaced the 100uf/150v with 100uf/450v overkill but it's done now. thanks so much for your help dude, really appreciate it. Thanks also G1, much appreciated.

Chuck.