Hi - newbie here, updating my beloved console and keeping it original as necessary.
‘62 Magnavox 9302 I’ve been working on has me perplexed and I’m trying to run down the issues.
New PS caps installed and checked.
Great sound.
Questions:
1. PT gets 150°F after 1 hr - what can I do to lower this?
2. Heater supply to pins 1 & 2 of the 6EU7’s reads 12 volts - is that right?
3. 6EU7’s plate voltages read 167, 176 (130 nom) and 200, 210 (160 nom)
Those are way out of spec - 30-40%
I changed a .047 coupling cap and there was no change.
How do I get these voltages down and how do I get the PT to run cooler?
How do I check the PT to be sure it’s not toast?
Thanks in advance; I searched extensively but no one had these exact issues.
‘62 Magnavox 9302 I’ve been working on has me perplexed and I’m trying to run down the issues.
New PS caps installed and checked.
Great sound.
Questions:
1. PT gets 150°F after 1 hr - what can I do to lower this?
2. Heater supply to pins 1 & 2 of the 6EU7’s reads 12 volts - is that right?
3. 6EU7’s plate voltages read 167, 176 (130 nom) and 200, 210 (160 nom)
Those are way out of spec - 30-40%
I changed a .047 coupling cap and there was no change.
How do I get these voltages down and how do I get the PT to run cooler?
How do I check the PT to be sure it’s not toast?
Thanks in advance; I searched extensively but no one had these exact issues.
You may have to use a fan to cool things down much.
The 6EU7 definitely uses 6V, not 12V. Are they in series?
The 6EU7 definitely uses 6V, not 12V. Are they in series?
My other Maggie’s don’t run that hot. I think 155-160 is far too hot.
My concern is it ran hot prior to the filter caps being replaced.
My concern is it ran hot prior to the filter caps being replaced.
These 9302’s stock are setup fairly cool for tube & component longevity. Another reason a hot PT doesn’t make sense if output is <10 wpc out of 15.
Older electronics was designed for a lower AC line, around 110V, and you may even have a high AC line, 120V or even more.
You could try dropping the value of C1. Looks like 40uf on the schem. Is that what you're running?
jeff
C1 is the very first ceramic, I’ve got .01 mf/1000v on my schematic:
Attachments
Sorry it's C2A, the first one after the 5U4. The schem. I was looking at is really small.
jeff
With everything being about twice as the design value, it almost looks like a 110V unit running at 220V!
Jan