Rectifier used in HMV 2022 Record Player.

[Old Sparky]

This is a contact cooled Bridge Rectifier, and I'm always suspicious of these.  At the moment it is putting out about 240vDC, and I've traced the loud hum produced to the fact that the reservoir capacitor is o/c, but would I be advised to replace the rectifier with a modern silicon bridge type (with appropriate series resiistor of course)?

[ppppenguin]

I would replace the rectifier as a matter of course. Opinions may differ.

[Murphyv310]

Hi.
Although we have a dislike for selenium rectifiers, I've found that the ones in radios and record players to be far more reliable than in TV sets.
Once you've fitted a new capacitor of the same value as the original and all works o.k. after a decently long soak test I'd be inclined to leave it as is. Your choice though to go silicon and faff around with limiting resistors.

[Terry]

You obviously never had much to do with all those Bush radios that used them, Trevor!

[Murphyv310]

In fact I did Terry. Duff caps and output stages drawing excess current due to valve pluggers not replacing Leakey caps were the culprits in many cases.
A rectifier lasting many long years is the proof of the pudding.
No one ever considers the peak voltage realised with silicon, it's always a compromise between normal running voltage and initial switch on voltage...... Has other components been suitably selected for this or left to the suck it and see brigade.

[Old Sparky]

The contact cooled rectifier in the 2022 may be OK. There was a loud hum when I first switched the amplifier on, having found an ECL86 to replace the missing one. This was due to the reservoir and smoothing caps both being low value (<16uf instead of 32uf) and, perhaps more importantly , having high ESR. The rectifier produces readings on the ohms ranges of my DMM which make no sense to me, but then I've forgotten what readings to expect from such devices!

[Craig]

Selenium rectifiers are still made. Got replica ones for a Bletchley Park restoration from http://www.gdrectifiers.co.uk/ .

[Murphyv310]

Hi.
The ESR is less important with a 50 or 100Hz ripple than the Khz ripple found in SMPS.
I will never forget the increased unreliability of sets that had a BY100 fitted along with a surge limiter, all sorts of nasties happened with capacitors failing and resistors going open circuit due to the much increased initial voltage.

[Old Sparky]

Thanks for the info. about 'GF Rectifiers, Craig. I didn't know such devices were still made!

[Old Sparky]

I have refitted the original rectifier to the HMV record player, and am now getting ca. 330vDC (measured with my DMM). At the moment there is no sound from the amp.,but the severe hum has gone since also replacing the Reservoir & Smoothing Capacitors. More to investigate ASAP!