Traynor YBA-2B Bass Mate guitar amp repair

When buying broken tube radios I was offered to have a look on an "old guitar amp" which "was bought for kids 20ish years ago to learn guitar and wasn't played much". Didn't expect this to be a real tube Traynor Bass Mate lol.

According to the internet this 6V6 version with a solid state rectifier was manufactured by Yorkville Sound LTD in late 60s, then they switched to EL84 version.

The amp was serviced and tested. I had my band student played it a bit.  It sounds amazing! It will be probably looking for a new home, not listed yet though.

Below are some technical details on the repair and maintenance. 

Speaker

The 15 inch speaker has a huge square ceramic magnet and labeled 15B54-8B DWC1. It also had a date written on a cone, probably someone was servicing the amp. DW appears to belong to RSC (Radio Speaker of Canada). The speaker looks original to me, internet agrees with me saying that RSC speakers were widely used in Traynor amps. I'd presume someone was replacing the cable as they drilled a hole from inside and put a cheap RCA jack with crimp connector which I had to replace with a good 16 gage cable.

List of maintenance

For the maintenance I performed the following:

1. Cleaned pots with DeoxIT
2. Attached a good 18 AWG 10ft 3 prong power cable with a ground wire connected to the chassis
3. Installed a new speaker cable with golden RCA jack and plastic plate preventing cable from sliding up and down
4. Replaced electrolytic capacitors
5. Placed "safety" 470Ohm resistor across external speaker jack so the amp always has some load 
6. Adjusted voltage drop resistors to accommodate to a modern higher AC voltage
7. Replaced old diodes with 1N4007 ones
8. Swapped a cable from input jack to first tube grid with a shielded cable
9. Installed 0.1 Ohm resistors in series with 6V6 cathodes, so I can measure current via each tube
10. Installed LED bulb

Finally I glued front metal plate and tolex to where they should be, covered the amp with a bit of bee wax to make it shine a bit. Old chicken head knobs found to be loose so I replaced them as well with exactly same ones. 

The output 6V6GT are running a bit hotter to me, at about 110% of their spec power, but I assume it's pretty common for guitar amps. Heater voltage is measured at 6.7V AC which is inside 10% tolerance. 

The original 6V6GT turned to resonate on some notes. Luckily I had a pair of great pair of matching Westernhouse 6V6GT tubes without this issue.