Orange 100 mkii

[Perkinsman]

Hi guys, this is another amp with no sound. The preamp filaments are on & I get 3.2vac on pins 4&5 of each preamp tube, but no other significant voltages on the preamp tubes. The 4 el34’s don’t even have filaments lighting up. All tubes have been tested & are good. The “on” lamp doesn’t even power on (lamp is good). Is anyone familiar with these amps to know what the most likely problems are?

[BobK]

Do you have the schematic?
Those amps have many on board fuses, seems like a number of them blew. That's not a good sign.

[Perkinsman]

All of the fuses are good. I just ran a line out from the fx send to another amp input & got good, strong, clear sound. Does this mean that the preamp is ok & the problem is in the power amp? I couldn’t find a schematic named Rockerverb 100 mkii. I’ll keep hunting.

[BobK]

Now I'm a bit confused.
I guess I misunderstood what you meant by "no other significant voltages on the preamp tubes"?

A good signal out the FX loop send could just mean a bad interrupt on the FX loop IN jack. Did you try plugging the FX out to the FX in with a cable?

[Perkinsman]

Sorry to have confused you. I realized that I must have measured using only vac. I remeasured using dc & plate voltages ranged from 150-250 on the preamp tubes & 450 on the power tubes so it seems they’re working. I plugged into the input, ran a line from the fx send to another amp and got good sound. Switching to the fx return yielded no sound. Jumping from fx send to fx return yielded no sound either.

[BobK]

No worries!

There are a few different Orange 100 amps.

The Rockerverb 100, for example, has many fuses on the board. Like 6 of them I think and they're not all together.

Since you said that the output tubes don't light up, have you checked to see if you have filament AC?

If you don't have AC at pins 2 & 7 of the output tubes then I still think it's more than likely that there's a burnt fuse or two on the board that maybe you don't know is there. Maybe, anyway...

[Enzo]

This^^^

In post #1 you said the power tubes did not light, so of course the power amp won't work.

And what matter is that you have 6vAC between pins 2 and 7. VOltage to ground from either pin means nothing.

When you checked fuses, did you just look at them, or did you remove each fuse from the holder and measure it with your ohm meter. The heater fuse is likely to be higher current. Also, were any of the fuses ceramic instead of clear glass? They are usually white. They do not change color, so just beuing white tells us nothing. AGain you have to remove them from the holder to measure resistance.

[Jazz P Bass]

Not sure if it is even close but here is the Rockerverb MKI: RockerVerb MK1.zip

[Perkinsman]

This^^^

In post #1 you said the power tubes did not light, so of course the power amp won't work.

And what matter is that you have 6vAC between pins 2 and 7. VOltage to ground from either pin means nothing.

When you checked fuses, did you just look at them, or did you remove each fuse from the holder and measure it with your ohm meter. The heater fuse is likely to be higher current. Also, were any of the fuses ceramic instead of clear glass? They are usually white. They do not change color, so just beuing white tells us nothing. AGain you have to remove them from the holder to measure resistance.

See post #5 updated last night. I had previously lifted one leg of each fuse & all tested for good continuity. This morning I read your post & decided to pull each fuse & re-test. Sure enough, FS3 was open. The silkscreen (& fuse) says T12.5A 250v. Is this a actually a 12.5 A fuse??

[doombass]

See post #5 updated last night. I had previously lifted one leg of each fuse & all tested for good continuity. This morning I read your post & decided to pull each fuse & re-test. Sure enough, FS3 was open. The silkscreen (& fuse) says T12.5A 250v. Is this a actually a 12.5 A fuse??

The schematics in post #8 include the power board schematic for the the 100W model. FS3 and FS4 are the heater fuses and indeed T12.5A.

[Perkinsman]

If the heater fuse was blown, how could I have got 150-250vdc on all preamp plates?

[doombass]

I suppose you mean the 3.2VAC on pins 4 and 5? That's because FS4 is probably intact and the centertap grounded so you'll have the 3.2VAC there. You are missing the 3.2VAC fed through FS3.

[Enzo]

If the heater fuse was blown, how could I have got 150-250vdc on all preamp plates?

Absent a schematic, we might assume the preamp tubes are running on a separate supply.

Heaters: If they light up, they must be getting power, regardless of a meter reading. When measuring heater supply always read ACROSS the tube heater, not from each end to ground.

[BobK]

The heaters and the HV are fused separately, so no mystery there.

[Perkinsman]

I didn’t realize that there can be hv on a tubes plate & no filament voltage but now I do.