73 Silver face Twin Reverb ?

[gtrplayr1976]

Anyone know how to test a reverb transformer on a 73 Twin ?

[überfuzz]

First thing I'd try is channel 2 aka VIBRATO channel.

(Maybe you could drop just a tiny bit more info on what you've done so far.)

[m-fine]

What is yor problem/symptoms? Have you replaced the cathode resistor on the 12at7 to a larger value yet?

[MWJB]

Determine turns ratio, just like you would for a OT ('cause that's just what it is), by applying a small AC voltage to the RCA plug to the reverb tank (secondary) & measure voltage developed accross primary (tank & 12AT7 driver tube removed, amp unplugged from wall, use 2 meters - one to actually measure voltage applied to RCA jack, the other to read voltage accross primary). Or, check out some specs on replacements & you may find a ball park dc resistance for the primary (measured from B+ supply to 12AT7 plate wires, usually red & blue wires - e.g. the Hammond quotes this as 1065ohms).

Turns ratio should be from 45:1 to 53:1.

First stop is to ALWAYS try a new/known good tank, transducer failures are very common.

[gtrplayr1976]

Ok...I have some buzzing on the bass end (like a speaker , but it's not) . I have replaced a lot of components, mostly caps. It buzzes through both channels, and for 100watts it doesn't seem that loud to me, but I don't hear so well anymore. If I can think of anything else I will post that also.

Thank you all for the help.

[überfuzz]

*Not knowing which caps you've replaced.* If it hums on both channels it's probably not the reverb transformer. Caps you say. Have you poked around in the filter? Bad filter caps can cause hum, but more 50/60 Hz, not like you described your hum.

Edit: By the way, buzzing on the bass end. Would that be a low key buzz..?

[gtrplayr1976]

*Not knowing wish caps you've replaced.* If it hums on both channels it's probably not the reverb transformer. Caps you say. Have you poked around in the filter? Bad filter caps can cause hum, but more 50/60 Hz, not like you described your hum.

I replaced nearly every cap including filters. It isn't a hum...more of a buzz, but only when I hit the bass strings is it noticeable.

[überfuzz]

Ok, does the level of the volume pot effect the buzz, high level more buzz response? If so it could be as simple as bad power tubes, unmatched tubes could maybe give the same effect. When did you replace them, were the replacement tubes matched properly?

Any how, like I said you're not likely to find the gnarly in the pre amp. The channels are separated. Look in the power section or the inverter. After the pre amp.

[gtrplayr1976]

Well as the amp gets louder ,so does the buzz . The tubes were new ,and matched JJ 6L6s.

[überfuzz]

Mhmm... back to the drawing board I guess. But just to make sure. Try the old tubes and see if it effects the buzz.

Have you measured and voltages in the amp? What did you get. (Be mindful if you never done it before. You might get ZAPPED quite harshly.)

[gtrplayr1976]

Oh I know all about the zapp...lol. I can check the voltages again ,and record the. Any particular voltages I should look for ?

[überfuzz]

If the tubes are ok, start checking around the power sockets. (Does the buzz follow the tone you playing or is it one pitched?)

Well, you can actually check a lot of things by probing the power sockets. Always check for both AC and DC if you looking for gnarlys. Particular voltages..? Check them all while you're at it.

Pin 1 - Jumper connection, negative.
Pin 2 - Heaters
Pin 3 - High voltage, close to or plate
Pin 4 - High voltage, close to or plate
Pin 5 - Negative
Pin 6 - High voltage
Pin 7 - Heaters
Pin 8 - Ground - Should be a big fat ZERO.

[gtrplayr1976]

The buzz doesn't change pitch . I'll check these this evening after my real work ,and record them.

[überfuzz]

Ehh... Could be that it's a 50/60 Hz 'buzz' you hearing?

Good luck with does measurements!

[gtrplayr1976]

And that would mean ? Thanks for the info, and help.