Tube Amps / Music Electronics
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|10/3/2004 1:37 AM|
||Volume is low - controls dont work|
Hello - I just finished another 5e3 (my 1st one is doing fine) I still have some work to do on the cabinet but I wanted to see how it sounded so I fired it up and here is the problem im having.
The volume is very low, even with everything turned all the way up it sounds like a car raideo. with everyting turned all the way up when I back off the volume from 12 to 10 on the channel im pluged into I have no volume at all. I switched all the tubes with ones that I know are good and ive looked over the wiring on the pots and the inputs & it all seems good.
I need some help with this one : thanks ; JOE
|10/3/2004 2:35 AM|
I'd check the 100k resistors off pins 1 & 6 of V1 and the 56k/100k off 1 & 6 of V2.
I had those 100ks from V1 switched w/ the 100 ohm resistors on V4 and the volume was super-attenuated. After fixing that little mishap everything was back to full volume.
|10/3/2004 1:06 AM|
Get an audio generator and inject audio into the grid of each stage starting with the final output section working your way backwards. As you go to each prevous section, the audio signal should get louder in the speaker because you are adding additional stages of amplification to the signal path. When you find the section where the signal gets quieter, you have found where your problem is.
I highly recommend the old tube type audio generators made by HP that can be found at swapfests for about $25. You don't have to worry about accidentally blowing them if you connect their output across B+ unintentionally. An indispensible tool for amp builders.
|10/3/2004 8:36 PM|
Do you have a couple model numbers in mind?
>> I highly recommend the old tube type audio generators made by HP that can be found at swapfests for about $25. You don't have to worry about accidentally blowing them if you connect their output across B+ unintentionally. An indispensible tool for amp builders.
|10/5/2004 12:24 AM|
I use an HP model 200CD. I can accurately dial in anything from 5 to 600,000 cycles. If you do RF work on receivers this model will operate beyond the frequency of most IF's which is nice. It also has a variable output which is a must. This particular model is usually referred to as their "extended range" model because of the 600K capability.
|10/3/2004 6:49 PM|
I looked over all the resistors both on the board and all the others, they are all the values that they are suposed to be. Ive been staring at the layout and the wiring for hours looking for a problem but I dont see one, that dosnt mean theres not one there. im not sure what to do next, could a capacitor be bad? I keep hoping to see someting ive done wrong but so far I havent found it.
|10/3/2004 7:14 PM|
give us some voltage readings on all the tubes. that will probably give us a clue.
be careful poking around in there...!!!
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