two quad 303's both draining power

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03-Jun-2019 12:19 PM

jackdelang UK

jackdelang UK

Posts: 14

I have revised one and the other one swapped TR3. On  initial start up 240 watts  on one and 140 watts on the other. I can't see any deviations in readings from board to board -6 boards in total. Made a Dim Bulb Tester (DBT) which lights a 40 watt at appx 75% full brightness. Don't have an oscilliscope. Something stupid ..I'm at loss
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03-Jun-2019 12:43 PM

jackdelang UK

jackdelang UK

Posts: 14

OK - i've checked the original RCA transistor ( That i swapped out -TR3) and put it back & now the DBT is strobing when the amp is plugged + its pulling 290 watts> I am using a plug-in pwer tester to get the watts readings.
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03-Jun-2019 03:25 PM

PeteUK

PeteUK

Posts: 12

Are you saying both amps are faulty?

The wattage figures for both are way over the top for quiescent conditions.

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03-Jun-2019 04:09 PM

PeteUK

PeteUK

Posts: 12

Is your plug in tester operating reliably? I'd check this before going further, it doesn't seem to tally with the earlier results of your bulb tester.
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03-Jun-2019 05:27 PM

jackdelang UK

jackdelang UK

Posts: 14

hi pete the tester is good. Both machines were working..
just call me Midas.. 

These BC556B transistors came in different flavours .. could they a problem? - different letters after 'B'

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03-Jun-2019 08:51 PM

PeteUK

PeteUK

Posts: 12

I doubt it Jack, maybe you've trapped or shorted a wire in the PSU area. Have you been able to check any voltages? Any signs of overheating?

I've blown one up before, see my video! https://www.youtube.com/watch?v=e095s6TAbcE

Maybe it will help...

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04-Jun-2019 08:58 AM

jackdelang UK

jackdelang UK

Posts: 14

Good morning,  Yes, overheating - i wont leave it on for more than 2 seconds but the top transistors on the  back (TR1L & TR2L?) start to heat up. This leads to the middle board.

The wiring diagrams doesn't show jumpers connecting the  transistors on the back. No shorts found between the shell and rear transistor pins.( or shell)

i dont understand exactly what dada means when he describes the pin out of the regulator board.

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04-Jun-2019 09:01 AM

jackdelang UK

jackdelang UK

Posts: 14

I've scoured you tube for information. Just proving  how manipulated their search returns really are as i should have seen your video a thousand times already
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04-Jun-2019 09:27 AM

jackdelang UK

jackdelang UK

Posts: 14

PeteUK - Great video by the way.  Why did you use those brown caps?
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04-Jun-2019 10:34 AM

jackdelang UK

jackdelang UK

Posts: 14

i replaced the top transistor and re-attached the chassis together and hit the power - R123 *68ohm smoking. Now replaced with a 1A 68ohm. but what made this happen tr101?
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04-Jun-2019 11:00 AM

EJP

EJP

Posts: 1605

Static power consumption of a 303 with no signal applied should be under 15 watts. Check your wiring. I don't know what you mean by 'wiring diagrams don't show jumpers connecting transistors on the back', as there are no wiring diagrams for the power transistors, but there certainly are wires there and they are certainly shown as connections on the schematic. If you've left them out, put them back.
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04-Jun-2019 11:58 AM

jackdelang UK

jackdelang UK

Posts: 14

What i mean is on the heat I see wire connecting all the brown leads. There are three.
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04-Jun-2019 12:56 PM

EJP

EJP

Posts: 1605

And your question about that is?
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04-Jun-2019 06:23 PM

jackdelang UK

jackdelang UK

Posts: 14

I'm replying to your nto knowing what i meant by jumpers @EJP
Anyways the other machine testing with the Dim Bulb - Initially its bright for less than half a second then goes very  dim for about One Second before getting bright again.

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04-Jun-2019 07:07 PM

jackdelang UK

jackdelang UK

Posts: 14

But i have a question about that.. The jumpers.. Would it matter if you connected these at the boards instead would it change anything?
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04-Jun-2019 07:51 PM

PeteUK

PeteUK

Posts: 12

I'm at a loss with your terminology. What exactly do you mean by jumpers? I can't understand what you're decribing.
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04-Jun-2019 08:53 PM

jackdelang UK

jackdelang UK

Posts: 14

What I mean is - at the back of the amp on the heat sink the Five transistors. There's wire connecting the brown/white + brown/red + brown wires = linking them..
Jumpers
Strappers.

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05-Jun-2019 01:55 AM

EJP

EJP

Posts: 1605

> Would it matter if you connected them at the boards?

Yes. These connectors carry high currents, which you don't want anywhere near the PCBs.

I don't know why would you want to change it anyway.

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05-Jun-2019 03:02 PM

jackdelang UK

jackdelang UK

Posts: 14

A theoretical question for my fundamental understanding of DC circuits. So the wires joining all three brown wires connected to the transistors on the back plate couldn't be connected at the board end and wired from there as single wires X3 - ?
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06-Jun-2019 02:27 AM

EJP

EJP

Posts: 1605

It's not a DC circuit. It's an AC/DC circuit, and the AC component brings electromagnetic radation into play, even in theory.
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06-Jun-2019 10:14 PM

jackdelang UK

jackdelang UK

Posts: 14

so thats why they strap the wires together at the transistors.
also - whats running off AC then?
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