Traynor YVM-1 to YVR-1 mod

[V2a]

YVM = Yorkville Voice Master
YVR = airport code for Vancouver, which is where I am located.

Bought this amp on a road trip. 1967. Four identical inputs for 'voice' (mics).
Who want see me turn it into JCM800-ish guitar amp?

 

[V2a]

Obvious first steps: replace original filter caps and two-prong cord. But who wants to deal with a permanently attached power cord?

New filter caps. Two-prong power cord and accessory plug removed.

New fused power receptacle in place of the accessory plug. Yes, you can fit a square peg into a round hole. Ground switch removed, and power switch moved away from power tubes.

 

[JackBootedThug]

Nice keep going…..

 

[Kapo_Polenton]

I say go Plexi on this one.. maybe with a PPIMV..then have a few of your voicing mods wired in on switches. Maybe mid pot ground lift so it has extra grind.

I wish I never sold my old Traynor. Did a few small " Marshall Mods" to it and replaced the two prong for a three prong. The damn thing shocked me once while playing so I knew I had to change that cord asap. Sold it for like 500 bucks so I could finish some basement stairs. Bad move.

 

[V2a]

The stock amp uses 7027A tubes. The octal tube sockets didn't even have terminals for pin1. But the primary impedance of the gigantic output transformer measured 3.5-3.8k, so it's probably taken from the Traynor YBA. Perfect for EL34s...

 

[V2a]

I say go Plexi on this one.. maybe with a PPIMV..then have a few of your voicing mods wired in on switches. Maybe mid pot ground lift so it has extra grind.

I wish I never sold my old Traynor. Did a few small " Marshall Mods" to it and replaced the two prong for a three prong. The damn thing shocked me once while playing so I knew I had to change that cord asap. Sold it for like 500 bucks so I could finish some basement stairs. Bad move.

If you have a chance, pick up a YBA-4. Thank me later....

 

[V2a]

Eyelet board cleared and cleaned. New components/circuits loaded onto the right side of the board, including new caps for negative bias supply, new screen resistors, phase inverter plate resistors and coupling caps.

Bottom left: a PCB holding a dropping resistor and filter cap for the preamp. I use modern radial electrolytic with long life expectancy (10,000+ hours) whenever possible.

 

[V2a]

PS. this will compete with Friedman Vintage but will not cost 3k. It'll be closer to 2204 than 1987, however.

 

[V2a]

The stock amp had a coupling cap between (each) input jack and grid of first gain stage. Initially, I kept that in there. Used shielded wire to board-mounted cap, and added a 33k grid stopper on pin 7 of the tube socket.

My wiring colour code for tube sockets:
- brown for unshielded grid wires
- yellow for cathode
- blue for plate.

Follow the wires to find:
- first gain stage cathode: 2k7 R with bypass cap
- first gain stage anode/plate: 220k plate with bypass cap to remove some high end hiss
- plate coupled to front panel gain pot.
- output of gain pot fed to input of second gain stage (with shielded wire and 91k grid stopper)
- second gain stage cathode: no bypass cap. lower value than Marshall's 10k cold clipper (4k7, I think)
- second gain stage anode: 100k R

anode Rs: 1W
cathode and most other Rs: 1/2 W

 

[V2a]

The initial build.
- ultra-fast diodes added to rectifier.
- adjustable fixed bias
- current-sense resistors added for bias measurements
- tube-driven effects loop
- other stuff.

 

[Kapo_Polenton]

PS. this will compete with Friedman Vintage but will not cost 3k. It'll be closer to 2204 than 1987, however.

You had me at "vintage" .. looking forward to seeing how it turns out.

 

[midnightlaundry]

Transformers are giant.

 

[V2a]

OT primary impedance measures 3k8 - perfect for EL34.
Problem: stock octal socket (left) was missing Pin 1, which is need for EL34 suppressor grid. Replacement Belton socket on the right.

 

[V2a]

 

[V2a]

Next problem: EL34s draw more heater current.

Solution: replaced stock 22AWG heater wire with 18AWG wire.

 

[Techdeth]

Excellent