Put one probe on the OT CT and the other probe on the plate. This gives you the voltage difference across one leg of the primary without having to subtract. This is your best bet with only 1 volt meter. This eliminates the effect of voltage drift and timing affecting the measurement.
It's made me want a super! Sounds so good, 4x10 is a real magic combo. Quite loud and heavy though, very clean until serious volumes. They're so undervalued right now, BF supers are available all day long for sub 2k here so I'm not jumping at anything... but eventually I'll grab one!
I saw a video where the repair tech had pretty much the same amp and he would lift and remove a section at a time of components and heat the board and remove the wax along with wiping it with alcohol. What a process to do this but it seemed to work out well.
I saw a video where the repair tech had pretty much the same amp and he would lift and remove a section at a time of components and heat the board and remove the wax along with wiping it with alcohol. What a process to do this but it seemed to work out well.
I love adding a 1r at pin 8 of the power tubes to the ground. Then you measure mv across the 1r, and that matches your ma for biasing. Safe and easy. On all my future builds, I'll be adding banana jacks on the chassis for convenience and safety
Yeah I've seen people talk about it, but I've never done it. I try to avoid soldering to the chassis, especially in crowded areas but my new chassis iron is more nimble. Maybe my next order I'll buy some 1ohm's and save for a rainy day. Though I don't really see the value over just biasing with a bias probe. Easier, doesn't require opening the amp up to check/confirm bias is fine. It's just these 70's with the cap from pin 5 to pin 8 to ground that messes it up.
@YeatzeeGuitar on my last build, I ran a wire from each pin 8 to a banana jack mounted on the chassis. 3 banana jacks mounted in a row, with a 1r between jack 1 and 2 and a 1r between jack 2 and three. The middle jack has a wire that runs to a ground lug, and the two end jacks connect to the wires coming off the pin 8 wires. Then, install the bias pot, accessible from the outside of the chassis . Works great. Understandable you.wouldnt do this to a vintage amp, though, lol . My buddy alligator clips a 1r in to do the bias. But the probes works great too
A bad center tap ground on the PT will cause the problem. Ground the direct to chassis like they did in BF panel days. Grounding to the heavy transformer bolts is a common fault.
Interesting! The ground looked solid, I always check those, but if you see the first / second video of this amp's series you'll see the 3 prong ground was on a transformer bolt and it came loose. I did that one directly to the chassis, I guess maybe as common practice I should just convert all of those to chassis grounds going forward
Sounding great and appreciate all this insight. So, harkening back to your first vid in this series, where you said you got the amp “cheap”, do you still think it was a good deal for you? I suspect that answer may change as to others, like me, who are not doing all these self repairs/upgrades.
Put one probe on the OT CT and the other probe on the plate. This gives you the voltage difference across one leg of the primary without having to subtract. This is your best bet with only 1 volt meter.
This eliminates the effect of voltage drift and timing affecting the measurement.
Sounds fantastic!!
It's made me want a super! Sounds so good, 4x10 is a real magic combo. Quite loud and heavy though, very clean until serious volumes. They're so undervalued right now, BF supers are available all day long for sub 2k here so I'm not jumping at anything... but eventually I'll grab one!
One of my favorite BF fenders for Les Pauls Fantastic sounding amps. I need to grab one while they’re cheap as well!
I saw a video where the repair tech had pretty much the same amp and he would lift and remove a section at a time of components and heat the board and remove the wax along with wiping it with alcohol. What a process to do this but it seemed to work out well.
I saw a video where the repair tech had pretty much the same amp and he would lift and remove a section at a time of components and heat the board and remove the wax along with wiping it with alcohol. What a process to do this but it seemed to work out well.
I love adding a 1r at pin 8 of the power tubes to the ground. Then you measure mv across the 1r, and that matches your ma for biasing. Safe and easy. On all my future builds, I'll be adding banana jacks on the chassis for convenience and safety
Yeah I've seen people talk about it, but I've never done it. I try to avoid soldering to the chassis, especially in crowded areas but my new chassis iron is more nimble. Maybe my next order I'll buy some 1ohm's and save for a rainy day. Though I don't really see the value over just biasing with a bias probe. Easier, doesn't require opening the amp up to check/confirm bias is fine. It's just these 70's with the cap from pin 5 to pin 8 to ground that messes it up.
@YeatzeeGuitar on my last build, I ran a wire from each pin 8 to a banana jack mounted on the chassis. 3 banana jacks mounted in a row, with a 1r between jack 1 and 2 and a 1r between jack 2 and three. The middle jack has a wire that runs to a ground lug, and the two end jacks connect to the wires coming off the pin 8 wires. Then, install the bias pot, accessible from the outside of the chassis .
Works great. Understandable you.wouldnt do this to a vintage amp, though, lol .
My buddy alligator clips a 1r in to do the bias.
But the probes works great too
The weird solder color is indeed from mixing leaded with unleaded solder. Those typically form weak/brittle joints.
Mmm, good to know. Everything I work on is vintage so leaded solder to begin with.
A bad center tap ground on the PT will cause the problem. Ground the direct to chassis like they did in BF panel days. Grounding to the heavy transformer bolts is a common fault.
Interesting! The ground looked solid, I always check those, but if you see the first / second video of this amp's series you'll see the 3 prong ground was on a transformer bolt and it came loose. I did that one directly to the chassis, I guess maybe as common practice I should just convert all of those to chassis grounds going forward
Sounding great and appreciate all this insight. So, harkening back to your first vid in this series, where you said you got the amp “cheap”, do you still think it was a good deal for you? I suspect that answer may change as to others, like me, who are not doing all these self repairs/upgrades.
This is not my amp, it was a customers.
@@YeatzeeGuitar Good deal for the customer then? 😉
@@adamkrauss303 no clue what he paid, but in general vintage super Reverbs are excellent buys.
Good deal! 🍻