mesa rocket 44 help

[etneccas]

I have no heater VAC on v1 and v2 but have it on v3 and v4............

[alexradium]

they are in DC voltage

[etneccas]

I see it now I downloaded a schematic......The amp's power tubes are redplating though I have the followimng voltages and could use some guidance troubleshooting pin 2 -11vdc pin 7 483vdc and pin 9 452 vdc

[shortcircuit]

I see it now I downloaded a schematic......The amp's power tubes are redplating though I have the followimng voltages and could use some guidance troubleshooting pin 2 -11vdc pin 7 483vdc and pin 9 452 vdc

can you post the schematic for us??

[g1]

Bias sounds ok, but plate voltage is crazy high.
https://music-electronics-forum.com/...0&d=1258342282

[alexradium]

leave tubes out until you get the plate voltage right,start measuring from the HV secondary AC,then check diodes and resistors,ground connections.

[drewl]

Mesa runs their old EL84 amps insanely hot and they eat output tubes.

Install a bias adjust pot/circuit and set bias to proper level.
You probably need new output tubes.

[g1]

Mesa runs their old EL84 amps insanely hot and they eat output tubes.

Around 400V for this model as far as I know. Schematic shows 380V. He is measuring 480V plate. I can't see that as normal for this model.
Not saying adjustable bias is not a good idea, just don't think the 480V at the plates is right. Maybe oscillation.

[rockon1]

Yeah as drewl mentioned they run them insanely hot. My DC-3 was 420VDC on the plates and only -11 as designed. No tubes would run less than 110%. The neg grid voltage needs to be at least -14 not -11 vdc thats not enough. That said 483vdc is WAY above design- unless the OP measured without the tubes in place? Bob

[etneccas]

My Bad the volt measurements were without the power tubes in....Pin9 is 320vdc and pin 7 is 400vdc the functioning but is very crackily and distorted on the contour channelive swapped the preamp tubes around and still have the problem There is a copper foil shield on V2 that tube base makes a similiar sound of cracking when I chopstick it I'll try to retension the socket

[rockon1]

My Bad the volt measurements were without the power tubes in....Pin9 is 320vdc and pin 7 is 400vdc the functioning but is very crackily and distorted on the contour channelive swapped the preamp tubes around and still have the problem There is a copper foil shield on V2 that tube base makes a similiar sound of cracking when I chopstick it I'll try to retension the socket

OK thats about spec at 400vdc. The bias is just tooo low from the factory. Had the same issue with my DC-3. Any tubes I tried (even low current draw) were over 100% dissipation! Eventually modded the bias supply with help from guys here. As far as crackling- you might have bad solder joints on the sockets or just dirty/loose ones. Disclaimer- Dangerous voltages inside even unplugged. Do not go messing around inside unlerss you know how to discharge the capacitors!
Bob

[etneccas]

Retensioned the socket and reflowed the socket pins one of them is still not shiny there is less craclking but still there V2 makes alot noise when chopstick it........

[rockon1]

Take a good look around. The amp gets really hot which translates into some decent temp swings on the board. I use really good light and two pairs of readers (yep, probably looks ridiculous) when hunting for cracked solder joints.

[g1]

One thing I will mention about these is that the PI tube current affects the bias. So if you have a change in the bias condition out of the blue, it could be PI tube related.

[drewl]

That is correct, but when I have increased the bias voltage, lowering current draw, the PI cathode voltage remains the stated 3 volts.