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Old 18th May 2006, 01:19 PM   #1
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Default Quad 33 transistor replacements

Hello to all
Actually I have a 33 preamp (SN 89456) on which I made a total
recapping and thought about transistor substitution on preamplifier boards 12017 and 12019.
But there is a small problem: any transistor have marked number model on case.
I see on schematics them seems to be all BC109 but on my boards transistors have TO-92 plastic cases really different from TO-18 metal case of BC109.
I thought about BC546B as substitute for BC109 but I prefer take more infos before make a disaster:-)
Anyone have suggest for this?
Thanks in advance

MArco - Turin - Italy
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Old 18th May 2006, 01:44 PM   #2
Did it Himself
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They probably just never bothered redoing the schematic. The BC10x and BC54x series are same just the metal/plastic version.
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Old 18th May 2006, 03:22 PM   #3
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Hello Richie
many thanks for your clear and fast answer.
All the best.

MArco
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Old 20th May 2006, 06:30 AM   #4
big jim is offline big jim  England
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Default Quad 33

TR300 AND TR301 SELECTED LOW NOISE TYPE

TRY BC550C I HAVE MANY TIMES

GOOD LUCK
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Old 20th May 2006, 11:03 PM   #5
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Hi
Many thanks for your useful answer also.
Have a nice weekend. MArco
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Old 22nd May 2006, 11:35 AM   #6
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Hello,

In the Quad 33 units I have seen, there were BC109C, BC 109B, BC 114, E5270.

The BC109C is still available but I had a good experience with the BC550C, costing one-third of the BC109C. Especially on the disc pre-amp board, you would use a low-noise variety of transistor.

I am experimenting with op-amp based circuits to replace the disc pre-amp, tape I/O and tone control amplifiers. Of course, the Quad 33 has no symmetrical power supply and single 12V isn't exactly ideal for OPA604-based circuits, so I had to squeeze a new transformer and a +/-15V power supply in the confined space.

Sacrilegious acts, I know, but the unit had already been tampered with anyway.

Can anyone point at a decent replacement for the stereo 2x50K Log volume potentiometer-with-mains-switch? The Quad representative in the Benelux has one for 40 euro...

Cheers,

Jacques
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Old 22nd May 2006, 02:45 PM   #7
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Hello Jaques

>Especially on the disc pre-amp board, you would use a low->noise variety of transistor.
It is my goal, I think after a caps replacement that this phono section could be upgraded with new modern transistor change..

>Can anyone point at a decent replacement for the stereo 2x50K >Log volume potentiometer-with-mains-switch? The Quad >representative in the Benelux has one for 40 euro...

I saw sometimes on USA EBay shops this volume pot, other choose could be a simple pot with an external main-switch or considering a low current absorption no switch.

All the best..

MArco - Turin - Italy
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Old 22nd May 2006, 08:27 PM   #8
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In the Quad 33 units I have seen, there were BC109C, BC 109B, BC 114, E5270.
The BC109C is still available but I had a good experience with the BC550C, costing one-third of the BC109C. Especially on the disc pre-amp board, you would use a low-noise variety of transistor.
--------------------------------------------------------------------------------
Hello Jaques
after reading your useful infos this evening I have observe 33 board using a magnifing lens and I have seen that some of the transistors are really marked E5270 and now I have another question for you and others:
are BC550 /BC546B pins compatible with this old trans?

I make a search on Net but I haven't found nothing, obviously I could follow the PCB traces to identify which are Emitter or Collector but if someone could or would help me I'll be really glad.
Have a nice night all.
MArco
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Old 23rd May 2006, 09:46 AM   #9
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Buon giorno, Marco!

TO-18 (BC 109) and TO-92 cases are practically pin-compatible. In case of doubt, one can always look up a datasheet (even by Google). Many vendors offer datasheets on-line. Just as an example, search for BC546 on it.farnell.com

This diagram is a bottom view:

Hoping this helps,

Jacques
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Old 23rd May 2006, 10:26 AM   #10
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Bon Jour Jaques!

many thanks for your useful infos.
I'll see on datasheets for these substitute transistors the correct pins orientation.

Merci beacoup.

MArco
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