Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Ariel tube fanatic on January 02, 2025, 10:59:17 am
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Hey All,
After a recent cap change, the rectifier does not light up
Things i've done:
1. verified that the 5y3 is good, tried another, both won't light up
2. high voltage checks out fine, i created a diode bridge and the amp works fine bypassing the rectifier
3. i'm getting 5vAC between the two Yellow wires
4. caps are oriented the right way
5. checked all grounds for continuity, they read fine.
6. fuses check fine
i'm at a loss as to why it won't light up and work, happened after the cap change but i haven't changed any wires or cut anything.
attached is the layout, the layout i have is page 4, schematic is page 1.
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The only thing a 5Y3 need to light up is 5 volts on pins 2 and 8 .
Socket pins send no voltage to 5Y3 base or in other words, pins 2 and 8 of the tubes see no voltage.
Or you'll have to tighten the contacts in the socket, which is too loose.
Did you read pins number the right way ?
Before caps change, is the amp was working fine ?
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Layout page 4 show a one red and one yellow wire on pin 2 and 8 not two yellow
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Layout page 4 show a one red and one yellow wire on pin 2 and 8 not two yellow
Look at the schematic to understand why.
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3. i'm getting 5vAC between the two Yellow wires
But are you getting 5VAC between pins 2 and 8 of the rectifier socket? There's a fuse involved.
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Solved, the red wire from recrifier socket to the board filter cap wasnt making good contact, replaced the wire and all is good now
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Solved, the red wire from recrifier socket to the board filter cap wasnt making good contact, replaced the wire and all is good now
Great ,
With that bad contact you read 5 VAC on tube socket before ?
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Yeah i did, the socket was fine, but i wasnt reading 5vac on the board, yet when chexking rhe wire i got continuity, really strange, now that it ia replaced evsrything is fine
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I suspect the OT is bad, voltages are geeat across the board but i'm getting distortion as i turn up the volume and not much happening after 3 oclock
The amp came to me with a burnt screen dropping resistor ( the 5.1k one) a bad capacitor (was probably damaged along with the burnt resistor) could it be that the OT died as well?