Dumbleland Special 150w ser#009 Schematic

[martin manning]

I'll try to get a clip up this weekend.

Sounds interesting! I'm convinced that if the original has the Sunn 1200 OT, it's running distributed load as it was designed to do.

[rccolgan]

I'll try to get a clip up this weekend.

Sounds interesting! I'm convinced that if the original has the Sunn 1200 OT, it's running distributed load as it was designed to do.

Martin - what would one look for to confirm/deny that it's running as a distributed load?

[martin manning]

I make that conclusion based on the 6550 tube characteristics. With 500V on the plates the screens have to be lowered, and why would you not use the DL taps if you are using that Sunn OT? It's possible to use a FWB with a CT PT to get a half-B+ supply for the screens, but that's 100V too low. A look inside would be required to know for sure.

[martin manning]

Here's a better photo of the Triad R-25 A. Designed for two-phase rectifier, 400-0-400.

[rccolgan]

I make that conclusion based on the 6550 tube characteristics. With 500V on the plates the screens have to be lowered, and why would you not use the DL taps if you are using that Sunn OT? It's possible to use a FWB with a CT PT to get a half-B+ supply for the screens, but that's 100V too low. A look inside would be required to know for sure.

That's why I want to help. Does this help at all? And what more do you need to see

[martin manning]

The power supply filters seem consistent with this schematic (Sunn 1200S): https://el34world.com/charts/Schematics ... _1200s.pdf

[Roe]

Here's a better photo of the Triad R-25 A. Designed for two-phase rectifier, 400-0-400.

yes, that would make for higher voltages than 500vdc, probably around 530-560vdc.

on the 500v amps, a 500R shared screen resistor seems used (instead of a choke), together with 1k individual screen resistors

[rccolgan]

would this suffice as a PT alternative? BTW I have chassis files readily available if anyone wants to take on doing a run for TAG. This amp is on my to-do list for sure

Screenshot_20230101-123254.png

[martin manning]

would this suffice as a PT alternative? BTW I have chassis files readily available if anyone wants to take on doing a run for TAG. This amp is on my to-do list for sure

Yes, and that 120V 100mA secondary would make a nice +/- 160V supply for a CF driver ;^)

What about the OT? Hammond 1650W for up to 280W? Load line power at 550V with DL is 250W.

[rccolgan]

would this suffice as a PT alternative? BTW I have chassis files readily available if anyone wants to take on doing a run for TAG. This amp is on my to-do list for sure

Yes, and that 120V 100mA secondary would make a nice +/- 160V supply for a CF driver ;^)

What about the OT?

Sweet!! OT Markings are:
28-1312
606108
so a Mercury Magnetics MM-1200S-OT is a direct replacement. Hammond 1650W is close but not the same.

choke markings is 17-7520 (Sunn 1200S as well) so a Hammond 194G would get us very close.

[martin manning]

See above, Hammond 1650W would be fine.

[martin manning]

Funny thing about the Hammond PWDP13227 PT, it says 800V CT, but it does not show the CT on the data sheet. :^\

[rccolgan]

Funny thing about the Hammond PWDP13227 PT, it says 800V CT, but it does not show the CT on the data sheet. :^\

Well shoot.. I didn't notice that before! I can email them tomorrow if you don't

[Smitty]

No center tap. You can make lightning with this power supply. 3000V???

SB200.JPG

https://www.hammfg.com/electronics/tran ... sic/pwdahl

https://www.qsl.net/wa0kke/manuals/SB-200%20Manual.pdf

[Roe]

would this suffice as a PT alternative? BTW I have chassis files readily available if anyone wants to take on doing a run for TAG. This amp is on my to-do list for sure

Yes, and that 120V 100mA secondary would make a nice +/- 160V supply for a CF driver ;^)

What about the OT?

Sweet!! OT Markings are:
28-1312
606108
so a Mercury Magnetics MM-1200S-OT is a direct replacement. Hammond 1650W is close but not the same.

choke markings is 17-7520 (Sunn 1200S as well) so a Hammond 194G would get us very close.

Piemme Elektra does a Sunn OT: https://shop.piemme-elektra.it/Products/8339