[AMRadio] Help..need info on Thordarson multimatch driver T15D82

[wwd at netheaven.com]

In <5.0.2.1.0.20020424210936.00ac67c0 at pop.mindspring.com>, on 04/24/2002 
   at 09:13 PM, Bob Login <jlogin at mindspring.com> said:

>Hi Bill, Thanks for info.....others are telling me that the PCCP are for
>the plates of the driver pp tubes and that the xfmr has a 500 ohm output.
>So I will try to run it backwards feeding in at 500 ohms and connecting
>the PCCP to grids of the 813 pp class B mod....what do you think??? 73
>Bob,  AA8A

First off, do a turns ratio determination by appying 10vac to one winding
and measuring all the others. Now you know what you have, save the
current-carrying capacity of the individual windings. That you just have
to guess at- based on the overall size of the transformer.

Step-up, step-down - does it really matter? Can anyone suggest why it
might?

Are you running those 813s in 'screen-driven triode mode'? This mode would
presumably require more current thru your 'unknown' driver transformer, so
might be a problem. Place an ma meter in the common return and start off
real easy? Why not, since this will avoid the need for a regulated screen
ps. 

I'm really not directly experienced with this, just throwing out some
thoughts.

Why not do a home brew with some smaller tubes than 813s? Triodes before
tetrodes/pentodes. Walk, then run- as a concept.  Seeing screen grids
vaporize in a pair of Class C 4E27s is not fun (personal failure #xxx). I
should have at least connected the s2, s3 and Plates all together (triode
mode variant) which would have been more stable. You live, you learn.  
0o\

Good luck,
Bill    K2AME

>At 08:19 AM 4/24/2002 -0400, you wrote:
>>In <5.0.2.1.0.20020423221617.00ab1410 at pop.mindspring.com>, on 04/23/2002
>>    at 10:27 PM, Bob Login <jlogin at mindspring.com> said:
>>
>> >  Hi, Building a class B mod and have this driver xfmr. It says 15W
>> >multimatch driver. It has plug-in jacks on its side and solder connectors
>> >on the bottom  ...three are marked 500ohms A, B, C and across from them
>> >are P-C-C-P terminals. The label says T15D82 or possibly 32? seems more
>> >like 82....Need info on how to hook it up?   Would like to use my 32V2
>> >500 ohm mod output to drive the Class B.    Thanks, Bob, AA8A
>>
>>Are the C-C connected together ( 00.0x ohms)? If infinity then they expect
>>you to do so. Would there be any sense in adding some series resistance
>>here? What is the dc resistance of P-C? Compare this to the 500 Ohms dc
>>res to get a sense of the P-C impedance. You would LIKE it to be on the
>>order of 3.5k each leg. This value works into my 4-125 grids push-pull. In
>>other words you would like the 500 ohm imput to be upped to 3.5k ohms or
>>even more.
>>
>>You may want to install loading resistors across each P-C winding to
>>smooth out the audio (etc).
>>
>>It is hard to imagine that it would be a step-down transformer. Then it
>>would be called a 'line' or '70.7v' transformer. Chances are you have the
>>real deal. I'll have a bit of digging to find my old Thordarson brochures
>>. . .

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