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D&A 12 TUBER PROBLEM

D

donemad

Active Member
Jun 21, 2008
104
1
26
HOPE SOMEONE CAN HELP ME WITH THIS,,,,,,12 TUBER PHANTOM ,, WHEN I KEY UP , IT SOUNDS LIKE CRICKETS, THINKING IT MAY BE THE KEYING TUBE. A LOT OF PEOPLE HAVE LOOKED @ IT & CAN,T SEEM TO FIND OUT WHAT IT IS ,,,,,,,ANY HELP PLEASE,,THANKS
 

sounds like you need to check all the tubes .a tube going bad can cause all kinds of funny sounds .thats where i would start .checking the tubes on a tube tester .

in the future buy a transistor amp .less problems for the money.these old tubers while they can be nice are kinda outdated and most arent working right .i have bought tube amps that only lasted a few keys befor they blew up .money wasted.

if they arent mint and working at time of sale i would stay away from them.good luck.
i havent seen many phantoms that actually worked good.20-30 years ago yes .these days ...no
 
YES,,,I CHECKED ALL TUBES ON A TESTER& ALL WERE GOOD BUT 1 & REPLACED IT WITH A NEW 1 ,BUT STILL HAVE CREKIT SOUND,BUT DID NOT CHECK THE KEYING TUBE..........
 
if its keying up then the key tube is ok .you might have another problem.
could be the caps in the power supply need replacing?
these amps are old enough for the caps to be replaced.if all the tubes check good that could be the next problem.hard to say .sooo many things can go wrong on those tubers .
contact alan at tubesplus.com
pick his brain a little ,he is very good with tube amps .
 
First of all be very careful as this amp has HIGH VOLTAGE in it. Remove the cover and set the amp on its side (transformer side down) to where you can see both the top and bottom. Key the amp and see if you can see anything arcing or what might be causing the noise. If you don't see anything turn the lights off in the room and then repeat the process. If it makes noise in a tube type amp most of the time it will also show an arc or make smoke. Look at the tubes to make sure that none of them are turning red inside or have fireworks in them. Check the tuners on the top and bottom side to see if they are arcing. Check the relays to make sure they are not arcing also.
You didn't mention if the amp is working (producing wattage) or not. Contrary to what has been posted the tube type amps are still very good to have and use......you just can't abuse them like you used to be able to when tubes were cheap. That and they require "tuning" and are not plug and play like the newer transisitor amps which do not require any intelligence to operate.
If you have the tubes eliminated as a potential problem then you move on to the caps, diodes, chokes, tuning components, and resistors.
Just remember the first comment I made about the HIGH VOLTAGE. It can hurt you but it can also kill you. Be careful.

BC

PS: I agree with getting in touch with Alan. He knows tube amps inside and out and is a top notch technician on them along with Browning and Tram radios.
 
yes the amp works,& it talks, but it just has a churping noise in my audio, like a cricket...other than that it works fine........
 
The noise is in your transmitted audio when using the amp? Does it do it with the mike gain turned off? If you cut the mike gain down some do others still hear it? On an outside chance, are you running a D104 amplified microphone?

BC
 
i can,t hear it ,,,,,,,,only on hi power i think ,does more out put on low power than hi power, but only crikit sound on trans. when i key up on hi side ,,,,,,,,like its not matched out or something,,,,,,
 
it shows to be puting out a lot more on hi side on my watt meter ,but to other people it makes me show less on hi than on low,,,i think it needs to be matched out on the bottom,,i dont have a dummy load,,,,or even know how to match it out ,,,i do know a little about eletronics,,,,and high volts.....
 
I think I would first check all the coax connections...anywhere there is PL259 to make sure they are tight and making good contact. Sounds like a strange problem. One thing to try....when it is doing it put your hand on the amp at the same time to see if it goes away. Maybe it is RF sneaking around in it?

BC
 
ok,i,ll try that.but how do i adjust the screw on the bottom? looks like it may go to the final tubes?...its a bright shiny screw thats adjust in or out....what does that do?
 

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