Wonderland/JM100 build

[norburybrook]

Lou,

I have the heater wiring disconnected from the bulb/6v connection so the bulb isn't in play.

I've got 100r to ground from each pin and zero cross the pins which is perfect as I've got artificial center tap 100R resistors to ground.

marcus

[martin manning]

Measuring as Lou suggests you should get 100R from each leg to ground and 200R across (asumming 2x 100R artificial CT) Try reconnecting the heater leads and see if you can figure out the indicator. Then connect the HT and see if you can get the 500VDC on the reservoir. Finally connect the bias supply. Test with the limiter in first each time.

[JazzGuitarGimp]

Zero across the pins is the problem. Assuming you have removed all the tubes and pilot light as I have suggested, you should be seeing 200-ohms, not zero from pin 2 to pin 7. If you've got zero there, then you are putting a dead short across your heater secondary, and this will most certainly blow the main fuse.

[martin manning]

Maybe the pilot lamp socket is shorted. Disconnect that and check it. That would be consistent with the lamp not working.

[norburybrook]

Zero across the pins is the problem. Assuming you have removed all the tubes and pilot light as I have suggested, you should be seeing 200-ohms, not zero from pin 2 to pin 7. If you've got zero there, then you are putting a dead short across your heater secondary, and this will most certainly blow the main fuse.

Sorry just re checked and it is 200R across the pins..oops didn't have the meter probes pressed hard enough.

I've connected the 6v and the pilot light is on :d


I've reconnected the bias supple and I have -57vDc at the pot wiper I'm just doing the 190's

m

[norburybrook]

Ok, connected the 190's and it blew straight away.

marcus

[norburybrook]

here's a close up of the rectifier board.

I can't see how the 190-190 going into the FWBR can short anywhere??

marcus rectifier board.jpg

Could the diodes be not up to the task? they just standard IN4007

Marcus

[ToneMerc]

Ok, connected the 190's and it blew straight away.

marcus

Was the standby switch open or closed when you connected the 190 volt leads to the FWB?

TM

[martin manning]

Progress on the filament string and pilot light.

Could the diodes be not up to the task? they just standard IN4007

1N4007 should be fine as they are rated at 1kV and will see about 1.4x the VAC, so ~400(1.4)=560V. What TM is getting at is if the standby was open when the fuse blew then I'd suspect a shorted diode. If it was closed then the problem is downstream.

[ToneMerc]

What TM is getting at is if the standby was open when the fuse blew then I'd suspect a shorted diode. If it was closed then the problem is downstream.

Exactly Martin ......divide and conquer.

TM

[dhudson]

Hey first post here, just like to point out your schematic and layout on pg.4 do not match at the 220uf caps and 220k r.
your problem may be in that area, if you could post a pic of the caps and wiring there may be helpful,
according to schematic those caps should be totem poled and resisters in parallel with each.


dave

[Charlie Wilson]

Hey first post here, just like to point out your schematic and layout on pg.4 do not match at the 220uf caps and 220k r.
your problem may be in that area, if you could post a pic of the caps and wiring there may be helpful,
according to schematic those caps should be totem poled and resisters in parallel with each.


dave

Indeed, the layout for the power board is missing a wire. There should be a diaganol wire under the board from the hot side of the first 220uf to the negative side of the second 220uf. The chassis ground then goes to the negative side of the first 220uf. Finally, the B+ and OT CT goes to the hot side of the second 220uf. Someone please verify this.
CW

[Charlie Wilson]

Ah, I just noticed Martins post. OK he reversed the diagonal wire that was missing on the layout. Never mind.
CW

[Charlie Wilson]

Deleted

[Charlie Wilson]

deleted