SBE SB2LA Amp Filament Transformer

[Amperex]

I have a SBE SB2LA amp with failed filament transformer. It failed open primary. I noticed it uses a Triad 553-F182U transformer. The amp uses six 6JE6C tubes with 2.5 amp 6.3 volt filament each tube. It uses two tubes in series for a total of 7.5 amps at 12.6 volts (6 tubes). I am using 6ME6 that draws 2.3 amps filament per tube. However the stock and replacement filament transformer is only rated 6 amps and no room for a larger filament transformer. Only alternate is to mount an 8 amp transformer off the back to meet filament current draw requirements. Think the new 6 amp filament transformer will be ok with .9 amps overload from the six 6ME6 tubes? At 2.5 amps per tube transformer failure is likely imminent with 25% overload, at 2.3 amps overload is 15%. I usually never go above 10% overload on a continuous duty load.

 

[Monk]

Is that the stock SBE transformer?
Or, just the one that was in there and failed?
Have you checked the load voltage?
Tubes don't have to run at exact voltage to work.
$30 isn't so much anymore...
RF Parts twice the price https://www.rfparts.com/166r12.html
More than one way to mount a transformer.

 

[Monk]

Have you considered 6 31lq6 three in series X2 across the 120 v AC input. No filament transformer needed.

 

[nomadradio]

Hmm. Three times thirty-one is only 93 Volts. Divvying 120 Volts from the wall three ways would put 40 Volts on each heater. Does jazz up the tube's power gain, but it's like nitrous. With no off switch.

The Hammond transformer shown will do the job. It's a 100 VA transformer and you'll only pull 85 more or or less.

73

 

[Amperex]

Have you considered 6 31lq6 three in series X2 across the 120 v AC input. No filament transformer needed.

I have new 6ME6 tubes

 

[Amperex]

Is that the stock SBE transformer?
Or, just the one that was in there and failed?
Have you checked the load voltage?
Tubes don't have to run at exact voltage to work.
$30 isn't so much anymore...
RF Parts twice the price https://www.rfparts.com/166r12.html
More than one way to mount a transformer.

Stock SBE transformer. Voltage is about 6.3 volts. It has 115 volt primary

 

[Amperex]

Have you considered 6 31lq6 three in series X2 across the 120 v AC input. No filament transformer needed.

The Hammond 167R12 is too large to fit.

 

[nomadradio]

Here's a toroid core transformer that would probably work okay with the two 6-Volt secondaries in parallel.

https://www.antekinc.com/as-0506-50va-6v-transformer/

It's an inch and a half thick and 3-3/4 in diameter.

73

 

[Amperex]

The Hammond 167R12 is too large to fit.

Too high diameter. I have 3.5" high.

 

[Amperex]

I assume transformer will be ok as nothing larger fits anyways. If fails I will install an Antek on back panel.

 

[nomadradio]

Good plan.

73