Hi all I have a hf31 fidelity record player here and the amp valve markings have worn off. The rectifier valve is the uy85 but only marking on the actual tri/pent ???? valve is 8! Please can someone help me identify this valve. Also dose anyone have a schematic for this player please? Thanks for helping if you can I hope so
Valve type
Hi,
If the rectifier is a UY85 them the other valve will be a UL84. Often the heaters were fed from a tap on the motor.
This was a "classic" line up being driven by a crystal cartridge.
BEWARE this will be a live chassis design with the chassis connected to one side of the mains supply so take great care when working on it.
John
Hi,
If the rectifier is a UY85 them the other valve will be a UL84. Often the heaters were fed from a tap on the motor.
This was a "classic" line up being driven by a crystal cartridge.
BEWARE this will be a live chassis design with the chassis connected to one side of the mains supply so take great care when working on it.
John
Thanks man. I noticed soon as I sore it that it would be, I am not a fan of going near these things when powered! When I looked at the valve inside I said to the owner that it is an el84 but was not sure because there is no triode infront of it for the smaller signal. so I looked at the rectifier and no numbers indicate a triode in there like the UABC for instance. So are the el/ul84's designed for small signals? Thanks for your help 🙂
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Fidelity HF31
Well no it is a power output valve,
But as it is being driven by a crystal/piezo pickup cartridge running into probably 1-2MΩ there will be enough voltage generated to drive the UL84 directly and give you about 2 watts of audio if you are lucky.
John
Well no it is a power output valve,
But as it is being driven by a crystal/piezo pickup cartridge running into probably 1-2MΩ there will be enough voltage generated to drive the UL84 directly and give you about 2 watts of audio if you are lucky.
John
Attachments
Thanks for your help guys. All is well, just added a double insulated flex and a simple swap of the filter cap but I was really amazed by the distinct lack of passive components in this thing! This was my first look inside one of these players. I knew the ul84 as an output valve but it threw me when I found it in such a circuit. As I have no knowledge of these pick ups, I wonder if you happen to know of a good link or even the good old book, where I might find an easy read to learn of them. If not I will give it a google. Thanks again for your help. 🙂
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