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Sets, Parts and Service Information Wanted (private buyers only, no swaps) If you need help obtaining components, sets or equipment, post a message here. Private buyers only - no traders. No swaps.

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Old 2nd Aug 2020, 7:36 pm   #1
cathoderay57
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Default Wanted 6EH5

Hello all, I'm repairing a Drake R-4B communications receiver for another Forum member. Checking the on-load voltages I'm getting a slowly rising dc voltage on grid 1 of the AF output valve 6EH5 as it warms up, rising to about +1.3v. I've disconnected the grid coupling cap but the voltage still rises so it ain't that. I've removed the valve and the grid voltage remains at zero therefore it cannot be a leaky valve holder. I've been unable to find a supplier of 6EH5 this side of the pond. A long shot, but I thought it would be worth putting out a request in case somebody has a decent one. Cheers, Jerry
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Old 2nd Aug 2020, 8:17 pm   #2
paulsherwin
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Default Re: Wanted 6EH5

Can you modify it to use something like an EL91? Even an EF91 is a possibility if you only need half a watt or so of output.
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Old 2nd Aug 2020, 8:55 pm   #3
John_BS
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Default Re: Wanted 6EH5

I think 6CA5 might be equivalent? There' a guy in Spain selling a NIB on Ebay.

John
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Old 2nd Aug 2020, 9:35 pm   #4
cathoderay57
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Default Re: Wanted 6EH5

Thanks for both suggestions. I'll hang on a bit in case anyone comes up with an exact replacement. The 6CA5 is pretty close, grid bias is easy to adjust if needed, other difference being 4.5k anode load impedance as opposed to 8k for the 6EH5 but unlikely to make much audible difference.
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Old 2nd Aug 2020, 9:40 pm   #5
turretslug
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Default Re: Wanted 6EH5

Would it be permissible to re-wire the valve socket for something like a 6AQ5 that at least retains a US flavour (flavor?). Cathode resistor/grid bias would need changing to suit, but should provide adequate service in a comms receiver. The 6EH5 consumes nearly 8W heater power, which seems a lot for something in a B7g bottle!
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Old 2nd Aug 2020, 10:09 pm   #6
cathoderay57
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Default Re: Wanted 6EH5

Probably a toss-up between EL90 (6AQ5), EL91 and EL95. All would be running at low anode and grid 2 potential (about 130v and 140v respectively) and so not producing their max output. All 3 would require a socket rewire which shouldn't be an issue. I've only got an EL95 so maybe I'll give that a go. I'm not even sure I should be worrying too much because the 6EH5 is only showing 5.1v on the cathode indicating a cathode current of 42.5mA, which is within the max spec for the valve. I'll run the set for a while and see if the current creeps up any further. Still interested in a 6EH5 if anyone has one. Cheers, Jerry
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Old 2nd Aug 2020, 10:55 pm   #7
yesnaby
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Default Re: Wanted 6EH5

https://www.ebay.de/itm/6EH5-TUBE-RC...QAAOSwT6pVqPB2

On eBay Germany, though valve is located in Spain!

The valve pins don't look too good though ....
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Old 3rd Aug 2020, 10:38 am   #8
cathoderay57
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Default Re: Wanted 6EH5

The owner preferred to keep the receiver original, so I've bought the spare identified in Post #7 - thanks for the tip, Yesnaby. Mods please close. Cheers, Jerry
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