Orange Matamp ORST 50w, ORST 100w?, OR100

[skylark]

Hello folks,

what is the difference between the ORST with 4x EL34 (has smaller Partridge trasnformers T149 (choke), T150, T151) and the Orange Matamp OR100 series (larger Partridge T147, T148, T149 transformers).
What were the Partridge trasnformers on the 50w ORST? Was there a 50w ORST and a 100w ORST?
I am trying to get an overview of the whole line-up, as it seems there were quite a few variations and models.

The amp that Hiwatt Bob posted here seems to be actually a 4x EL34 ORST, i am not sure if that is a later mod - seems like it had 4x EL34 tubes from the get go:
https://www.thegearpage.net/board/index ... t.1274758/

I have seen also other ORST with what looks like original 4x EL34 tubes. I'm curious, if it used the same trasnformers as the 50w ORST.

Thanks a bunch in advance for any input!

Best,

Skylark

[Gladmarr]

That looks to me like an ORST that was built after they had OR100 chassis built. They just plugged the two extra the socket holes.

[skylark]

Would you say the same about this - is it actually a 50w ORST (with Partridge T151 OT) that someone has been modded to run with 4x EL34?
Did the ORST 50w have also the Partridge T151 OT?

[Gladmarr]

Considering the screen grid resistors don’t look the same on the outer pair, I would say you are correct. That transformer looks too small to be a 100W transformer.

[LD50]

Yes you are correct.

The contemporary OR100 and ORST from 1970 both use the same choke and pcb.

A 100w uses T148 (G9978) OT, T149 (G9979) choke and T147 (G9977) PT

A 50w ORST uses T151 T149 (G9981) choke and T150 (G9980) PT

I have a whole bundle of pics of these.

The only other difference is the Drive pot and wiring which is simpler on the ORST.