Scott 222B output transformer : Compatibility and specs - diyAudio
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Old 5th July 2010, 02:45 AM   #1
k730292 is offline k730292  United States
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Default Scott 222B output transformer : Compatibility and specs

My otherwise near mint Scott 222B has been diagnosed with a bad OPT, a TRA 8-4-1. I have not been able to find a replacement, but do have access to a pair of Scott TRA 8-5-1s.

1) Are these OPTs compatible; that is will the TRA 8-5-1 function successfully in the 222B as a replacement for the TRA 8-4-1?
2) Can anyone provide specifications of the TRA 8-4-1 in case I need to have a new one manufactured?

Thanks for your time,

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Old 5th July 2010, 02:56 AM   #2
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Whatever you get, you want to get a pair...PP OPTs for EL84/6BQ5, somewhere 7-10k plate-to-plate.

The Scott OPTs are outstanding (we have 2 sets of these, 1 set in a functioning Class A triode build (a stunning amp), and 1 being rebuilt (power trafo failure)) so for same quality they are unlikely to be inexpensive.

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Old 5th July 2010, 05:14 PM   #3
k730292 is offline k730292  United States
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Planet 10,


The Scott 8-5-1s I have a line on are used in the Scott 222 C&D models which use 7189 output tubes. My failed Scott TRA 8-4-1 OPT on the 222B drives less powerful 6BQ5 output tubes. Do you have an opinion as to the suitability of using the 8-5-1 in place of the 8-4-1?

As an aside, perhaps, I have another 222B with significantly smaller 7-1 OPTs (~2/3 the size of the TRA 8-4-1 OPT). The smaller 7-1 opt unit has a earlier serial # then the unit with the larger 8-4-1 OPTs. Comments?

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Old 5th July 2010, 05:29 PM   #4
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The TRA 8-5-1s will be fine. Just make sure the mechanical mounting fit is correct.

Using 7189s in place of 6BQ5/EL84s is always OK. The other way around can be problematic. The 7189 is rated for higher voltages than the 6BQ5 is.
Eli D.
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Old 6th July 2010, 02:57 AM   #5
k730292 is offline k730292  United States
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Thanks- it as is I have understood: the 8-5-1 is OK electrically; the physical dimensions will be the determining factor. If I have to have the 8-4-1 rewound, I've been told the Essex TRA 8-4-1 winding is the same (or essentially so). Whatever, I'll get the 222B up and running. I appreciate everyones comments.

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