Bridge rectifier question

Hi all,

I'm working on my polytone amp and I want to replace the bridge rectifiers. The smaller is labelled "BR71A" and the larger is "BR121". Can somebody tell me what that means? I don't see those designations in my catalogs. One is for +/-24V rails and the other is for +/-31V rails.

Thanks,

Part Number = BR71A
Description = Single-Phase Full-Wave Bridge Rectifier
Manufacturer = Various
V(RRM)(V) Rep.Pk.Rev. Voltage = 100
I(O) Max.(A) Output Current = 2.0
@Temp (°C) (Test Condition) = 60
I(RM) Max.(A) Reverse Current = 5.0u
@V(R) (V)(Test Condition) = 100
I(FSM) Max.(A) Pk.Fwd.Sur.Cur. = 50
V(FM) Max.(V) Forward Voltage = 1.0
@I(FM) (A) (Test Condition) = 1.0
@Temp. (°C) (Test Condition) = 25
Package = BR-3p
Military = N

BR31 (3A, 100V bridge) is a cross reference for BR71A.

Thanks Dave.

So is a BR-121 a 12 Amp 100V?

BTW, I took your advice about the mask and the gloves - that fiberglass is very unpleasant

If it is, it must be a big mutha

I came up empty-handed with data for BR-121. You're sure that's the right part #?

By the way, did these bridges fail? You really don't need to replace 'em unless they've failed.

It says BR 121 on the side - it is much larger than the BR71A. I'm not sure if they've failed. The symptom is loud buzz regardless of preamp settings or input, so I thought I'd start by replacing the filter caps, the regulator caps and the rectifiers. I see one cap in the regulator that looks like it's leaking, but after thirty years (I bought it new!) I figure the amp deserves new electrolytics all around. I haven't tested the bridges yet because my hands are itching like crazy despite the gloves and I got away from it as fast as possible.

As always, thanks for your help Dave.

:sam: :sam:

We need a pizza emoticon!

itching like crazy

Click to expand...

See, that's why my skin still crawls when I hear the name "Polytone." I've been inside a few of those things :shock:

I'm sure there's a load of possible subs for that bridge, but I'd need to know the case style/footprint before I could recommend one.

It's 1.25" square and .25" thick and I checked again - it says BR 121.

:thumb:

[quote author="jrmintz"] The symptom is loud buzz regardless of preamp settings or input, so I thought I'd start by replacing the filter caps, the regulator caps and the rectifiers. [/quote]

FWIW, I had a similar symptom on my Ampeg Gemini amp... I know its seems completely unrelated, but I wound up recapping, redoing the rectifier section, etc... In the end it turned out to be a blown output tranny, so it may be worth checking for a short there before you go to deep...