BeoGram

Re: BeoGram 4002 6000 (AC motor) capacitor

yachadm — Tue, 31 Aug 2010 00:51:39 GMT

I ran a couple of tests - I put in the following capacitors (polypro 100VDC), and scoped the oscillations at 0TR1 collector

No capacitor - medium oscillations

10nf - bad oscillations

22nF - bad oscillations

47nF - medium oscillations

100nF - slightly less oscillations than no capacitor.

220nF - no improvemnt over the 100nF

I left the 100nF installed.

Other members advised me that they also don't have a capacitor there.

I'm going to hazard a guess that the capacitors were present on the early production units with the older square-type transistor, and when (on later production units) there was an Engineering change to the 2N3055, the capacitor was no longer required.

Re: BeoGram 4002 6000 (AC motor) capacitor

yachadm — Wed, 25 Aug 2010 07:33:22 GMT

Thanks Mika,

But I'd really like to be sure of this from someone who has one with a cap, and can tell me what is is ;-)

Menahem

Re: BeoGram 4002 6000 (AC motor) capacitor

tournedos — Tue, 24 Aug 2010 12:34:19 GMT

Mine doesn't have a cap there (and I see no traces of one having been there either).

Can't be too important... but I always use 100 nF for everything

BeoGram 4002 6000 (AC motor) capacitor

yachadm — Tue, 24 Aug 2010 12:28:53 GMT

On the AC motor units, there is a large transistor next to the motor - a 2N3055 - this is 0TR1 in the SM.

On this transistor is a ceramic capacitor which appears to be connected between the Base and Collector.

This capacitor does not appear in the SM.

On the unit I'm working on, this is broken, and I cannot identify what capacitance it is.

I presume this is to reduce oscillation, but how important is it really, if it is missing?

Menahem