OT transformer secondary issues

[ThisLifeILead]

When he mentioned the neon bulb test, he was NOT referring to the light bulb limiter, he was talking about a ringing test. Go to RG's Geofex site and find the transformer tester. Very simple.

Ahhh i see now the neon is critical for the test. but i think your right enzo. its super duper loud if there was a problem with the secondary windings i would have seen it when i was playing through it. i played it through a traynor YCV-18 with a massive eminence 18" driver. It shook the house :-)

[ThisLifeILead]

This is the condition i got it in. missing vol control, 2 coupling caps and 2 of the 4 tubes were shot. good jan 5751 in the input and a nice 12at7 in the P.I.
Reminds me alittle of how Garnet amps are wired with the bias supply and rectifier circuit on a vertical board. even the silkscreening reminded me of garnet amps.

[g1]

Agree with you that you must have taps one step from each other. Either 2&4, 4&8, or 8&16.
Forget what the labels say. The transformers may even be from something else. I doubt someone using perf board like that would have ordered custom xfrmrs from Hammond, but who knows.
The impedance you need on the primary side will depend on the operating conditions. You can plug your numbers into the calculator on nickb's site here: Interactive Valve Data Sheets
Also, you can run the amp into different load impedances. Each tap should give max. power at closest to it's proper load impedance.

[ThisLifeILead]

Also, you can run the amp into different load impedances. Each tap should give max. power at closest to it's proper load impedance.

thats a good idea. it would back up the measurements. but it seems like they are 2 steps away from eachother. 2/8 for both totalling 2800 ohms for the reflected load.
i contacted hammond about them and i gave them the marking info it had on it. Both the PT and OT were not typical models they would carry or make. nothing in their records came up. they were probably from a defunct amp company.

[Leo_Gnardo]

it would back up the measurements. but it seems like they are 2 steps away from eachother. 2/8 for both totalling 2800 ohms for the reflected load.

It seems unlikely but such "2 steps apart" transformers do exist. THD used to have a 2/8 ohm OT in their built-like-a-tank 5F6A Bassman copy, and still does in their Flexi-50 amps. On the Flexi's back panel, the speaker ohms switch is labeled 2-4 ohm on the low side and 4-8-16 on the hi side. Maybe not a 'zackly exact match but what they're doing is inviting those driving 4 ohms to use your ears, pick the one that sounds best and go with it. Haven't seen any damaged yet. Dam' good amp too!