[Jukebox-list] Hot Plate (6973)

[Jay Hennigan]

Carl Haines wrote:
> Ron Rich wrote:
>> Carl,
>>
>> If you don't see this on the list--please post it for me, as for some 
>> reason my posts to the list are going into hyberspace---just "fwd" 
>> this whole thing--TIA
> 
> I waited and this one never showed up on the list.  It looks like 
> something has changed with your email.  Your messages are now being sent 
>  with the body in HTML only.  Yahoo may have changed something with 
> their email that the mailing list does not like.  I'd be curious to hear 
> if anybody else on yahoo is having difficulty posting using Yahoo web mail.

I never even saw a delivery attempt on the admin interface here.  Please 
try to send in plain text if at all possible.

>> I think that what is happening there is that some of the "replacement" 
>> 6973 tubes were not built to mount as they do in that amp. I think 
>> what is happening is that something internal is getting too heated, 
>> and "bending" just enough to cause that problem. I have seen that 
>> problem too--but never with "real" 6973" tubes---perhaps I just wasn't 
>> looking??
> 
> This just helped motivate me to get a real set of 6973 tubes.  It is 
> possible that the tube was damaged previous to my ownership by being 
> used in an amp that needed to be recapped.  I have a 6L6 around here 
> that has a plate that is deformed from excessive heat.  The output 
> transformer in that amp had an open winding to go with damaged tube of 
> course.

On the 222 series Seeburg amplifiers, be sure that the negative voltage 
supply is working and producing voltages reasonably close to spec.  This 
power supply is a simple half-wave rectifier.  The early ones were 
selenium.  It supplies both the transistor preamp as well as bias to the 
6973 output tubes.  If this power supply fails or is marginal, the tubes 
will get cherry red and eventually take out the output transformers.

--
Jay Hennigan - CCIE #7880 - Network Engineering - jay at impulse.net
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