Monkeymatic Pinnacle #2 (Carvin X100 to BluesMaster)

[xtian]

I've launched my next conversion project. The donor amp is an early 80s Carvin X100, 100-watt 12" combo. This is not a X100B, although circuit was nearly identical to the X100B schematic. Was a pretty good sounding amp, especially the clean channel. But! It has made the ultimate sacrifice, and will now become the next Monkeymatic Pinnacle, a #183/BluesMaster inspired machine, like the one I documented here.

The PCB just barely fits--I had to rotate the PT 180 degrees so the wires don't crash. I have to punch new holes for the preamp tubes, because the old holes are hidden under the center of the PCB.

pinnacle1.jpg

[dorrisant]

I hope you don't mind sharing a model name.

[xtian]

Punching new noval holes into the steel chassis--not to difficult with the Greenlee punch.

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Grinding out the unneeded components...why'd they have to rivet them in? Easy, I guess. Anyway, Dremel with cutoff wheel makes quick work of them.

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But, man, drilling accurately on the sloped front panel is NOT easy. Even with my alignment tool clamped down hard, it still slipped.

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Good progress on populating the board.

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[xtian]

Heater string is strung. Most components in; remaining ones arrive tomorrow. My vacation got cancelled, so likely can finish this weekend.

carvin2.jpg

[xtian]

HT question. My PCB is designed with a FWBR for the Hot Rod PT, which has a HT secondary with red-red (no CT) = 332vAC unloaded. In practice, this gives me about 420vDC on plates.

The donor amp's PT has a red-ct-red secondary that measures 340-0-340 unloaded. That's 680vAC from red to red. If I omit the CT, and try to use it like the Hot Rod PT, amp I going to get 680 x 1.41 = ~950vDC on the plates? That cannot be right. So what am I miscalculating?

[martin manning]

No, you got it right. You can probably sub two diodes for the bridge rectifier and wire your board for FW.

[xtian]

Thank you, Martin.

[xtian]

I replaced the FWB with FW (a quad of 1N4007s), and everything is testing well, with about 420vDC at the reservoir (no tubes in), and the bias and switching voltages are testing good.

[xtian]

Clever Monkey Department: Instead of drilling holes for the standoffs, I attached the standoffs to the PCB, coated the free ends in JB Weld 2-part epoxy, set and clamped the whole rig into the chassis, and let it cure. Came out great!

pinnacle3.jpg

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Good progress today--everything is done except the front panel.

pinnacle2.jpg

[xtian]

After solving a couple of bonehead moves (3R dropping resistor instead of 3K, signal/bias wires to power tube pins 5 instead of 6) and one poor heater connection, this amp is up and running!

440v on plates, bias set around 50%, putting out 80 watts clean. Very low noise at idle. Sounds good so far, in the little strumming time I had.

pinnacle.jpg

pinnacle2.jpg

[pompeiisneaks]

wowza, looks excellent! I still wanna build one of those boards into my blues deluxe since it's been relegated to the corner all alone for so long

~Phil

[xtian]

Well! My ears are ringing. The EVM 12L sounds BEAUTIFUL in clean mode--no tweaks needed there. But the overdrive channel is too bright and biting, even though I've turned the HRM Treble control to zero.

There is a 470K||47p treble peaker leading into the OD circuit--I could try jumpering that out. And I'll try a different tube, maybe a 12AT or AY.

Any other mods folks commonly make to tame the OD high end?

[JazzGuitarGimp]

Hi All,

I am thinking about doing a small run of these boards in a few weeks. At this time, I can only provide a schematic of the board and a bill of materials for the board; unfortunately, this is all my time allows for. I realize a wiring diagram showing the board in the chassis, with wires to all of the off-board components would be really useful, and I apologize. So maybe this board should be thought of as a tool for upper-level-intermediate to advanced builders? You be the judge. Price will be $79.95 plus shipping. If you’re in the continental US, figure on about seven to eight dollars for shipping. Any interest?

Cheers,
Lou

[pompeiisneaks]

I'm interested, it will get me going on that blues deluxe

~Phil

[JazzGuitarGimp]

I'm interested, it will get me going on that blues deluxe

~Phil

Thanks, Phil, I am working on a few updates to the pcb, based on xtian’s findings in the amps he has built with it. Should be ready to go in a few weeks.

Lou