Allen model 75 organ amplifiers

[stormytaylor]

Anyone ever modify the power supply with damper diodes to bring up a slower B+ rise?

No one has modified the power supply for a slow B+ start up? The reason I'm asking is it would seem that the 75 has to cool down a bit before it is powered back on because the B+ is instant and it doesn't like that.

 

[vrusso123]

I started with two of them and now I have 5.

oooohhhhhh! surround sound!

KIDDING, jeez.

 

[buglegirl]

Hiya,

No one has modified the power supply for a slow B+ start up? The reason I'm asking is it would seem that the 75 has to cool down a bit before it is powered back on because the B+ is instant and it doesn't like that.

Allen 90's like mine have 5R4GY rectification.

I would guess you could look into a third party solution or using some smaller damper tubes you could tuck under the chassis. Although I am not sure if smaller ones would be up to the task amperage wise.

Frannie

 

[battradio]

No one has modified the power supply for a slow B+ start up? The reason I'm asking is it would seem that the 75 has to cool down a bit before it is powered back on because the B+ is instant and it doesn't like that.

http://tubedata.tubes.se/sheets/191/6/6DE4.pdf

You would most likely want to add a 2 amp filament transformer and would loose about 5 watts with the B+ drop and a lot of bass .

Instant on B+ won't hurt the tubes , it has been like that over 50 why change now .

 

[stormytaylor]

Mark,

Thanks for the reply. Maybe I'm so used to amp with rectifier tubes and being able to turn them off and right back on that I forgot that with a SS rectifier one must let the tubes cool a bit before turning right back on?

 

[stormytaylor]

Anyone have the schematic for the older version of the amp with the 3 vertical resistors mounted on the right portion of the top of the chassis? I've been told this version is different.

 

[stormytaylor]

New caps on order so I will be refurbishing two of these gems soon.