Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Bruce on October 17, 2016, 05:46:45 pm
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Going through amp last 4 days lots of stuff lose.broken wires from power supply to preamp harness,very cool way to make a amp pre on top ,below power. No power on preamp tube with 25 uf 25 volts ..replaced now works,question what is wrong with replacing the 4 100uf 150 volt filter caps with 100uf 450 volts.. the first cap was getting 430 volts second 300 third 200 and the last cap 100+ ... 150 volts not sure why so low they have never been touched ,one owner me... would 200 v or 350 v or 600v all work the same if all were 100uf I can't find this answer any were .. ..cheep made amp but not bad on designing some cool and smart ideas to the build ..all 1 meg pots ,real point to point, chassis very thin .box pressed wood all most card board.smalles reverb pan I have ever seen..a lot of cutting corners ..no way like fender or ampeg amps of same time period. Any other up grades or anything to improve sound ect thank for any respond
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Welcome!
I do not remember the DS50. Give us some clues. Schematic would be terrific. A tube line-up would be some clue.
_IF_ this is a 6L6-class amplifier(?), those 150V caps are WRONG. 150V caps are for low-power table radios, record players, and the $19.99 "guitar amps" sold around 1959.
If tubes have numbers like 25xx 35xx 50xx, then 150v caps would be correct (but go to 200V caps).
Fix it. Don't "improve" it. We have plenty of "good" amps from Fender and his copy-cats. The truly unique amps will fade away if we don't save them as-is (but healthy).
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Thanks 35 watt 2 6l6 3 12xa7 and 2 6cg7 has tremolo & reverb.my question is can you go over the rated volts ,say schematic calls for 100uf 150 volts ,what bad can happen if you go with say 500 or even 600 volts ? Now you have 100uf 500 volts what happens if any thing .... I get not messing with the uf ratings much and nothing less say 40 uf to 16 uf....but the effect on just higher voltage I don't get ...I think these amps were very cheap and the 4 filter caps are in series but the first cap is reading 400 plus volts .. I have 4 100uf 500volt caps, and I don't know what effect on other parts might be ..here is schematic below had to buy so anyone need this copy it.
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Your 500 volt caps will work just fine.
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> the 4 filter caps are in series
Yes, and 120V on each 100uFd cap.
A very odd way to do it. May be a combination of low-volt rectifiers and the low prices of 150V caps in the dying days of tube kitchen radios.
You "can" use four 100uFd 500V caps, but it will be a LOT more expensive. 150V caps are not hard to find.
You can't use one cap (as most amps do) without major re-wiring.
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PDF for Danelectro DS50
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Thanks for reply .schematic I paid for on line ,not sure if you can get it ,having problems keeping schematic it won't share
PDF for Danelectro DS50
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Been debugging danelectro ds50 .after replacing the 4 filter caps now I have a loud hum ,did not have ten minutes before new caps. Cap check out ok on peak atlas meter, 0 esr . Question is can cheap caps sound real noisey but not testing bad ???. Posted schematic last week ...Amp sounds pretty good for how cheaply it was made.. cap are elum never heard of them but don't want to spend $150 on sprauge on high end on a $10 amp ..diodes are also good ...please help this amp is about a day away from becoming garbage
Asl
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I merged your latest message into this thread so people would not have to search for the original thread.
New caps can certainly be bad. But it would be very easy to make an error replacing caps in this circuit. Double check. Measure some voltages. Show us a pic of your work.
EDIT... This amp is nearly identical to the Silvertone 1984.
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> don't want to spend $150 on sprauge
As implied, Danelectro's Purchasing Manager used the CHEEPEST floor-sweeping caps he could find. Skulking in the alley behind the radio factories scarfing surplus and rejects.
Will these fit?
http://hoffmanamps.com/MyStore/catalog/parts4.htm (http://hoffmanamps.com/MyStore/catalog/parts4.htm)
down, down, down....
100uf/350v Illinois 18.2mm wide x 38.3mm long - $5.78 each
mouser.com Search "TVA1420"
Vishay / Sprague - Leaded 150V 100 uF $7.15 each
15.875 mm dia 44.45 mm long
Do the bias cap (100uF 50V) too, it is important and isn't any fresher than the main caps. Yes, a 150V or 350V cap in a 37V job is over-kill. You could go Hoffman 100uf/100v Nichicon 10mm wide x 26.5mm long - $2.06 each(!)
Even five of Mouser's caps is just $36, not $150. Hoffman will ship 4+1 for $26 and actual postage.
Even cheaper: do you have dead/unwanted desktop PC power supplies? These usually have two 200V caps at 220uF-470uF. Two duds gets you the four main caps, although 2X to 5X "better" filtering than the original. Possibly way too big?
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Did all caps bigger than1.0 uf replaced 2.2 and 100k and put in 100uf 100volt cap diode ok but bypassed it to see if hum would go away ,did not. Everything worked out sounded very good ....then I did the 4 filter caps,and got a big hum ..put in many tubes all good and no improvement. About ready to hang it up back in garage. I don't expect to much but there has to be away to calm the hum ???
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after replacing the 4 filter caps now I have a loud hum ,did not have ten minutes before new caps.
That pretty much says that the act of replacing the caps caused the hum. Either bad caps or you put one in backwards or made some other error, either directly or indirectly.
If you can't find a problem by examining your work closely, maybe just put the old caps back in. Post some high rez pics and maybe someone here can spot something.
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Got it done ..replaced 2 preamp tube socket,replaced 2 100k resistors.4 new input jacks with 1 meg resistors in Chanel 1 & 2. . Took out ground switch and 3 prong plug and different filter caps witch did not do anything to take out the hum but the tube sockets made it fender quiet .and when you unplug guitar and leave cable in amp no noise at all ...add a few good solid parts make this amp a keeper.