RCA Calypso

fullrangeSR · 26th September 2009, 04:28 AM

I got this console in non-working condition (bad caps). The attachment is an approximation of the circuit ( I omitted the balance, tone and loudness). Any thoughts on the schematic?

DigitalJunkie · 26th September 2009, 05:29 AM

Other than the plate-to-plate feedback,it looks pretty standard to me. Should make a handful of watts.

azazello · 06:54 PM

Sorry, but where is the grid resistor /to ground/ of 6BQ5?

fullrangeSR · 27th September 2009, 01:42 AM

Quote:

Originally Posted by azazello

Sorry, but where is the grid resistor /to ground/ of 6BQ5?

There wasn't one...

azazello · 27th September 2009, 03:37 PM

OK....I'm sure that RCA is right!

fullrangeSR · 29th September 2009, 07:39 PM

Quote:

Originally Posted by azazello

OK....I'm sure that RCA is right!

It didn't seem anybody messed with the original circuit... The fact that the resistor is not grounded was the main reason for my starting this thread: while I'm not totally new to 'toobs', I'm still light years away from being able to understand all the nuances (doing the math, etc.)...

DigitalJunkie · 29th September 2009, 09:15 PM

Hum,I didn't catch that on my first glance.
It seems for sure that there should be a grid-leak resistor to ground,or else the bias point will drift at the least,or go into runaway at worst. Strange.

fullrangeSR · 30th September 2009, 02:32 AM

'Mystery' solved - thank you guys. You persuaded me to double-check the (complete) circuit, which I did and... The grid resistor IS grounded - through the balance pot... Oh well, another lesson learned...

26th September 2009, 06:51 PM	#3
azazello diyAudio Member Join Date: Aug 2008 Location: Bulgaria	Sorry, but where is the grid resistor /to ground/ of 6BQ5? Last edited by azazello; 26th September 2009 at 06:54 PM.

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26th September 2009, 05:29 AM	#2
DigitalJunkie diyAudio Member Join Date: Apr 2003 Location: Portland,Oregon Blog Entries: 4	Other than the plate-to-plate feedback,it looks pretty standard to me. Should make a handful of watts.

27th September 2009, 03:37 PM	#5
azazello diyAudio Member Join Date: Aug 2008 Location: Bulgaria	OK....I'm sure that RCA is right!

29th September 2009, 09:15 PM	#7
DigitalJunkie diyAudio Member Join Date: Apr 2003 Location: Portland,Oregon Blog Entries: 4	Hum,I didn't catch that on my first glance. It seems for sure that there should be a grid-leak resistor to ground,or else the bias point will drift at the least,or go into runaway at worst. Strange.

30th September 2009, 02:32 AM	#8
fullrangeSR diyAudio Member Join Date: Dec 2008	'Mystery' solved - thank you guys. You persuaded me to double-check the (complete) circuit, which I did and... The grid resistor IS grounded - through the balance pot... Oh well, another lesson learned...

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