Hiwatt DR103 blowing fuse

[Oddvar R]

Hi. I am just about finished with my take on the Hiwatt DR103. Problem is I am blowing the fuse and the light limiter lights up. When I disconnect the secondaries from the rectifiere, the light is dimmed. I am using two transformers from Hammond, and the reason is I had them. Could it be that these transformers aren't working on yhis build? I fail to see what the cause good be at this time.

[pdf64]

It would be helpful for you to clarify what exactly your take on a dr103 entails, eg a schematic.

[Oddvar R]

This one...

[sluckey]

I bet you connected the HT center tap (yellow wire) to ground. If so, disconnect the CT and tape it off. It's not needed and you can't connect it to ground and also connect the FWB rectifier to ground.

It's also very likely that the FWB is now defective because of this wiring error. Check all four diodes. Two of them are probably bad now.

https://el34world.com/charts/Schematics ... _dr103.pdf

[Oddvar R]

I bet you connected the HT center tap (yellow wire) to ground. If so, disconnect the CT and tape it off. It's not needed and you can't connect it to ground and also connect the FWB rectifier to ground.

It's also very likely that the FWB is now defective because of this wiring error. Check all four diodes. Two of them are probably bad now.

https://el34world.com/charts/Schematics ... _dr103.pdf

You are right Sluckey. two of the diodes are dead. By yellow, do you mean the Ct from the secondary high voltage?

[sluckey]

yes

[Oddvar R]

When I connect the rectifier like shown on the pic, the bulb limiter doesn't glow like chrismas, but glows as if the voltage is ok. Any views on this?

[sluckey]

When I connect the rectifier like shown on the pic, the bulb limiter doesn't glow like chrismas, but glows as if the voltage is ok. Any views on this?

Yes, that's still a correctly wired FWB. The original schematic by M. Huss works just fine too.

[Oddvar R]

So why those the former way blow fuses, but not the latter?

[sluckey]

Didn't you originally have the PT yellow wire connected to ground?

[Oddvar R]

Yes I did. I took it away, but it still blew the fuse.

I have some trouble understanding the DR103. Now I get 500v (aprox) on two filtercaps, but only about 16v on th b3 and b4? And very little voltage on the power tubes, but heaters work.

And the grounding circled in the pic, is that the way to do it?

[sluckey]

Yes I did. I took it away, but it still blew the fuse.

You have to remove the yellow wire ***AND*** replace the failed diodes. That yellow wire is the reason the diodes failed.

[mhuss]

Yes, the picture shows how the presence and bias grounds were wired on all original Hiwatts.

Did you check all four diodes?

[Oddvar R]

Yes, the picture shows how the presence and bias grounds were wired on all original Hiwatts.

Did you check all four diodes?

Yes I did. I don't get any voltage from the OT, so it might be some issues there.

I get 137v dc on the negative side of the 100uf cap.

[mhuss]

Yes, make sure you're getting the expected voltage from the secondary (while disconnected) before troubleshooting further down the line.