cws5
New Head-Fier
- Joined
- Jan 14, 2005
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I received a DV336 from a fellow head-fier last week, FedEx dropped the box (which broke a 6AS7), and the right channel is now dead except for buzzing.
I took voltage readings. I'm hoping that one of you tube amp DIYers with more experience than me can give me a few ideas as to the source of the problem.
Here's the relevant data from the readings with a sin wave feeding the amp:
INPUT TUBE (6SN7)
G2 .35v ac
P2 .028v ac; 7.2v dc
C2 .04 ac 24v dc
G1 .35v ac
P1 .32v ac; 88v dc
C1 .04v ac; 2.6v dc
As you can see, insufficient voltage is hitting the plate of one half the input tube (only 7v, versus 88 for the other half).
The OUTPUT TUBE is not showing any differences between halves that are not attributable to the input tube problem. That is, both plates are hit with 165v, etc. Also, both tubes light up properly (no problem with the filament voltage). And I've tried two different 6SN7s, both of which give me the same readings.
Here's a bit more info to help think about the plate voltage problem:
(1) the resistor between the socket's plate lead and the capacitor leading to the B+ reads the same for both working and non-working channels (27k ohms);
(2) because I do not get a zero reading but get 27kohm, there is continuity from B+ to the socket plate lead;
(3) at the capacitor I'm reading the full 165v.
So why in the world is only 7v hitting the socket's plate lead?
Your help is very, very much appreciated.
I took voltage readings. I'm hoping that one of you tube amp DIYers with more experience than me can give me a few ideas as to the source of the problem.
Here's the relevant data from the readings with a sin wave feeding the amp:
INPUT TUBE (6SN7)
G2 .35v ac
P2 .028v ac; 7.2v dc
C2 .04 ac 24v dc
G1 .35v ac
P1 .32v ac; 88v dc
C1 .04v ac; 2.6v dc
As you can see, insufficient voltage is hitting the plate of one half the input tube (only 7v, versus 88 for the other half).
The OUTPUT TUBE is not showing any differences between halves that are not attributable to the input tube problem. That is, both plates are hit with 165v, etc. Also, both tubes light up properly (no problem with the filament voltage). And I've tried two different 6SN7s, both of which give me the same readings.
Here's a bit more info to help think about the plate voltage problem:
(1) the resistor between the socket's plate lead and the capacitor leading to the B+ reads the same for both working and non-working channels (27k ohms);
(2) because I do not get a zero reading but get 27kohm, there is continuity from B+ to the socket plate lead;
(3) at the capacitor I'm reading the full 165v.
So why in the world is only 7v hitting the socket's plate lead?
Your help is very, very much appreciated.