EVH 5150 "ICONIC" (PR 5886)

[Mr_bibbles]

Looking for a schematic for the new 2x 12AX7 version of the 5150, 4x 6L6 80w head. Lost what looks like a DC heater for V1

Thanks!

[glebert]

I've fixed a couple EVHs that lost the DC heater voltage because they got goop onto the power resistors causing them to fail. In those cases replacing the power resistor fixed the problem.

[Mr_bibbles]

I've fixed a couple EVHs that lost the DC heater voltage because they got goop onto the power resistors causing them to fail. In those cases replacing the power resistor fixed the problem.

Thanks but I don't think this is the case. I'm getting about 15v on one half of the heater V1, but the "ICONIC" version of the 5150 is vastly different than the others- SMD, 2x 12ax7 instead of 5, dual trace board...

[glebert]

Thanks but I don't think this is the case. I'm getting about 15v on one half of the heater V1, but the "ICONIC" version of the 5150 is vastly different than the others- SMD, 2x 12ax7 instead of 5, dual trace board...

Have you reached out to EVH or Fender?

[Delta362]

Just had one of these come thru in late January with symptoms of V2 not lighting up.

The tube heaters are wired such that V1 uses the negative -12V circuit, while V2 uses the positive 12V circuit. You'll need to pull the board to access the resistors on the underside below the big filter caps. Once the board was removed from the chassis, I pulled C51 and C53 from the underside to allow for removal of R28 and R30 without burning the big filter caps.

You'll probably find a failed 62ohm 5W resistor. I ended up replacing the two resistors, plus the two 15V regulators and D13. And put C51 and C53 back.

[Mr_bibbles]

Just had one of these come thru in late January with symptoms of V2 not lighting up.

The tube heaters are wired such that V1 uses the negative -12V circuit, while V2 uses the positive 12V circuit. You'll need to pull the board to access the resistors on the underside below the big filter caps. Once the board was removed from the chassis, I pulled C51 and C53 from the underside to allow for removal of R28 and R30 without burning the big filter caps.

You'll probably find a failed 62ohm 5W resistor. I ended up replacing the two resistors, plus the two 15V regulators and D13. And put C51 and C53 back.

Huge! I think this is the issue, found one of the two resistors OL. Glebert, you were correct as well, there is some factory adhesive on the metal oxide resistor to the DC heaters, probably why it failed. Sorry to have doubted you!

Thanks!

[dugdiamond]

Did anyone come up with the schematic?
I also have one on the bench with only about six volts dc to the heater on V2.... will have to lift the board and have a look-see!
Sure would like a schematic of the power supply. I don't have many amps with DC heaters come across my bench! The extensive surface mount is a little intimidating at first. Will need to break out different iron and Chipquick!

[glebert]

Can't share a schematic (it's at the shop and don't think I'd be authorized to anyway, the manager is kind of uptight) but if you have a failed resistor I believe EVH is now suggesting replacing with 3 watt parts instead of the 2 watters that were there.

Don't worry about the surface mount or anything, for these resistors it is old school through hole. Getting the board out and cleaning up the adhesive are the hardest parts.

[The Dude]

Yep. I usually replace with 3W. I usually also remove and reinstall any caps in the way and clean up all of the conductive glue.

[dugdiamond]

Ok, I havent been back to the shop to pull the board yet. So, it is fairly obvious tracing back from the socket that its these resistors? R28 & R30? That is a good clue but would like to still have a schemo to look over. Its been many years since I had support from FMIC, I did look for it upon FMICASSETS online and could not locate an Iconic schematic, plenty of stuff for the III but the Iconic is a little elusive. Overall, despite the interesting mix of thru hole and SMD design, it does appear that it is a fairly nice quality multilayered PCB. Of course these boards can be like pulling teeth if you are not careful when removing thru hole components. I have an excellent electric vacuum pump activated solder sucker with hollow tip. I usually will snip the component too and just remove the leads. Somewhere along this thread there was also mention of replacing regulators and a diode too? I will have to get back to the bench and follow the circuit. I obviously did not get very far tracing it backwards as the trace ended in a via to the opposite side of the board. i did reach out to FMIC/EVH support but have not received a reply yet. Seeing as this documentation has not found distribution outside of the regular channels, it appears to be fairly well locked down.
THANKS GUYS FOR POSTING YOUR REPLYS!
If I have any problems I will post again and seek some assistance.... Certainly, a step back to the future after spending so much time in tweeds, blackface and plexis. LoL!
Well I have an LDMOS RF amp project on the back burner too!!! The times they are a changing!
Thanks again!

[dugdiamond]

Ok just a quick update,,,,
Its been awhile since I have sought technical support from FMIC,,,,, They're not as cooperative as they once were with me. No love as far as receiving a schematic. Almost makes me determined to see that a schemo for this amp gets disseminated. If I had less of a life going on, I would trace out the circuit and draw my own schematic.
It is an interesting circuit. This amp does the signal phase inversion ala solid state to feed both halves of the tube push pull power amp. Definitely not for the tone junky purist that insists on no sand in the signal chain. Certainly the effects loop is going to be op amp buffered and the reverb is digital. Regardless, It appears to have the tone for its intended demographic. Tone wise its really not that bad for this type amplifier.

Anyways, Just wanted to document yet another failure of gooped up resistors under the board near the DC supply in between the filter caps, EASY PEASEY fix! I spent more time digging thru the shop trying to locate 62 ohm resistors than it did removing the board.

Man this amp has huge amounts of gain on tap! Crazy gain, like a SLO or an Uberschall or similar amplifiers!