SF DR sounds like "blown" speaker &n

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RonB
Junior tube assistant
Posts: 1
(2/27/04 11:03 am)
  SF DR sounds like "blown" speaker
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 I'm new to this forum, and not an amp tech. I have a ca. 1980 SF DR, which makes the speaker sound blown when volume is past 4. It doesn't get much louder, just creates more of this buzzy sound. It's not the speaker. I tested this speaker on a 100W Marshall and it's clear as a bell.

On the advice of a different forum, I replaced the output xformer, no change. Tubes have been tested ok at a local shop.
Should I recap the main board, or just the filter caps ? Any guidance to a rookie here is welcome.
 
Tiny Daddy
I will work on all amps
Posts: 514
(2/27/04 11:18 am)
  Re: SF DR sounds like "blown" speaker
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 Have you tried different output tubes? If one or both output tubes are no longer able to supply large currents they may still test good on some testers.
 
RonB
Junior tube assistant
Posts: 2
(2/27/04 11:29 am)
  RE:
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 Thanks for the reply, yes these were replaced and biased, no change in sound. Is this buzzy sound intententional in Silverface DR'S ? Iv'e seen alot of posts suggesting a Blackface conversion. I don't recall the one I had back in the day sounded like this. Should be fairly clear unless turned up high.
 
Tiny Daddy
I will work on all amps
Posts: 516
(2/27/04 11:43 am)
  Re: RE:
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 Have you checked the B+ voltage and the bias current?
 
RonB
Junior tube assistant
Posts: 3
(2/27/04 11:54 am)
  Re: SF DR sounds like "blown" speaker
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 Way over my head, not a clue how to do this. I guess I'll have to send this unit out for repair, now I can't turn it on, it is blowing fuses. Worked fine (aside from the tone) after I replace the xformer last night, now it blows, literally.
 
Tiny Daddy
I will work on all amps
Posts: 517
(2/27/04 12:10 pm)
  Re: SF DR sounds like "blown" speaker
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 I could fix it, e-mail hendersoATflash.net
 
RonB
Junior tube assistant
Posts: 4
(2/27/04 12:26 pm)
  Re: SF DR sounds like "blown" speaker
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 I'll contact you. Thanks
 
RonB
Posts: 5
(3/4/04 3:14 pm)
  SF DR sounds like "blown" speaker
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 OK, I had the amp "repaired" by a local shop and still no change in sound. The amp just goes in complete overdriven sound as soon as I turn it past 3 on the volume. Why does this SF DR sound completely different from a 65 DR Reissue ?

Is this distorted sound what SF are supposed to be like ?

Do I need to have the Blackface Mod done to this amp ?
 
Tiny Daddy
I will work on all amps
Posts: 524
(3/4/04 9:59 pm)
  Re: SF DR sounds like "blown" speaker
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 The Blackface Mod is a good idea but mostly I expect the old electrolytic capacitors are causing problems.

EDIT: Should have said the Blackface mod is a good idea IF IT APPLIES TO YOUR AMP.

Edited by: Tiny Daddy at: 3/5/04 11:44 am
 
6G6
Junior tube assistant
Posts: 106
(3/5/04 9:50 am)
  Re: SF DR sounds like "blown" speaker
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 Tiny Daddy is right.
By replacing all the old electroytics you may eliminate your problem and the worst effect you can expect is ruling them out and having a good bit more peace of mind.
 
 
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