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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 21st Nov 2017, 2:40 pm   #61
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Default Re: Dr Dre Beatbox problems

I don't know about being the 'go to guru, Chris. The PSU still isn't working despite my having spent a considerable amount of time checking and reverse engineering it. Refugee, as for that o/c 10 ohm rsistor, it was due to a test prod slipping when I was taking some readings, which also caused an associated 1N4148 to fail s/c. The components concerned are the equivalents of d4/R11 (or D3/R7) in the PavoUK circuit diagram, so replacing them should cure a 'man-made' fault.
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Old 21st Nov 2017, 3:09 pm   #62
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Default Re: Dr Dre Beatbox problems

So we can log that as an "oops" fault that has been fixed.
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Old 23rd Nov 2017, 12:49 pm   #63
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Default Re: Dr Dre Beatbox problems

Yes indeed! WE all accidentally do things like that at times. However what i cannot understand is why I get collector to emitter short-circuit readings on both Q3 & Q4 (PavoUK Circuit). Both transistors check out OK, as do the two diodes D5 & D6. The emitters of Q3 &4 are common as in the Pavo circuit, but are returned to common -ve via a 1k5 resistor in parallel with a 4u7 capacitor, all of which are blameless.
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Old 23rd Nov 2017, 3:03 pm   #64
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Default Re: Dr Dre Beatbox problems

What instrument are you using to test the transistors in circuit with?
Some of those testers with a screen on them test with a short pulse and will read short circuit due to the discharged mains capacitors on the HT rail.
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Old 23rd Nov 2017, 6:47 pm   #65
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Default Re: Dr Dre Beatbox problems

I'm using my trusty M3800 DMM, not the Chinese component tester, as I always do when testing components in circuit.
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Old 24th Nov 2017, 12:38 am   #66
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Default Re: Dr Dre Beatbox problems

Quote:
Originally Posted by 'LIVEWIRE?' View Post
I may finally have a working PSU, and, hopefully a working Beatbox.
I'd suggest the owner hang on to it, its bound to become a collector's item as likely Dr. Dre is getting a promotion. Apparently since the Nobel prize committee awarded the prize for Literature to Bob Dylan, they are now obliged to award the Nobel prize for Medicine to Dr. Dre .
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Old 29th Nov 2017, 11:38 pm   #67
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Default Re: Dr Dre Beatbox problems

With reference to my post #63 -No matter how many years (almost 47 in my case!) any of us have worked with electronics or what qualifications we have, clangers can still be dropped! I should have checked both of the 2SC2235 transistors seperately. One of them has a virtual s/c - actually about 6 ohms both ways round - between it's collector and emitter, hence the readings I was getting. Two new 2SC2235s, plus posssible replacing the two FR107 diodes across said transistors C-E junctions should cure the fault, though what caused the transistor to fail s/c I know not.
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Old 4th Feb 2018, 11:43 pm   #68
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Replacing the components mentioned in post # 67 didn't get the PSU working again, depite the fact that one of the two 2SC2235 Transistors was so obviously faulty!
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Old 11th Feb 2018, 11:28 am   #69
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Default Re: Dr Dre Beatbox problems

Having been in contact with the owner of the Be since my last post, and been told that she doesn't want to proceed further with this repair, the PSU is now 'on the back burner', though I may come back to it out of interest later, if, and when I have less to do than at present. In the meantime thanks everyone for your assistance. I'm just sorry that, between us, we weren't able to get it working again!
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