bewildered by protection relay circuit

[samgraysound]

Sorry I use spice(s) only when cooking in the kitchen...

We have a logical paradox... You tell me you measure 65V RMS across the transformer, but do not get the expected as much as 90V peak driving the gate circuit.

It could be something obscure like the transformer CT  J1 is not the same 0V "ground" as as the JFET source 0V ground.

This is physics not magic so the answer is something simple and logical, while it will seem a lot more logical after you find it.

Probably  a bad connection somewhere, as I suggested earlier confirm the integrity of associated connections (like transformer CT).

It's always something.

JR

New day! I calibrated my oscilliscope quickly with my DC bench supply. On the scope the secondary voltage is approx 85vac p2p. The wave at the junction of D3 and D4 is little less then 40.

I breadboarded the circuit with all new components and hooked it up to the transformer. Everything acts exactly the same as on the pcb.

I tested connection between the transformer ends and ct, those are there. I measured voltage from each end to ct. 32vac RMS.

I emailed Ashdown and asked for the V+ and V- voltages. They said they should be +/-80v.  I have +42.5 and -48.5. The preamp board is supposed to have +/-15 and it is low as well.  So new theory, it's the PT. I emailed Ashdown and asked for secondary voltages so I can confirm.

 

[abbey road d enfer]

I emailed Ashdown and asked for the V+ and V- voltages. They said they should be +/-80v.  I have +42.5 and -48.5. The preamp board is supposed to have +/-15 and it is low as well.

Looks like you have a Euro PT!

 

[JohnRoberts]

yup...  I suspect the bass amp is a little puny too....

JR

 

[mjrippe]

Looks like you have a Euro PT!

Or worse, is there a 120/240 switch?  Sometimes it is implemented in a "clever" way, such as which slot you put the fuse in in the IEC inlet.  Or someone rewired it and didn't put a sticker on the outside.

 

[samgraysound]

Looks like you have a Euro PT!

*swearing incoherently*
*smashing things in the shop*

yes there it is barely visible in faded sharpie, 230 50/60hz V A.C

 

[samgraysound]

Or worse, is there a 120/240 switch?  Sometimes it is implemented in a "clever" way, such as which slot you put the fuse in in the IEC inlet.  Or someone rewired it and didn't put a sticker on the outside.

I don't think there's a switch. Only one set of primary wires. Checked inside the iec/fuse assembly.

 

[samgraysound]

The problem with taking only my most frustrating problems to The Lab is that they are always 100% my own error. So my whole history here is just a list of dumb mistakes.

Thanks everyone for your help and patience.

My variac is a Ohmite "V.T." 4.(?)5 amps. (Cat. #VT5-F)

 

[JohnRoberts]

what doesn't kill us makes us stronger (smarter).

JR

 

[Gene Pink]

The problem with taking only my most frustrating problems to The Lab is that they are always 100% my own error. So my whole history here is just a list of dumb mistakes.

Thanks everyone for your help and patience.

My variac is a Ohmite "V.T." 4.(?)5 amps. (Cat. #VT5-F)

Don't you mean "My Powerstat is a..."?  ;D ;D ;D

Check one more thing. Look around the primary side of the power transformer for extra wires. You might luck out and have a dual voltage primary.

Happy you got it figured it out.

Gene