DSE D-3800 P/S

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VK7HH
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DSE D-3800 P/S

Post by VK7HH »

My D-3800 died last night... though, mostly my fault...
It suffered a short circuit on the output of the P/S.

Voltage is no longer regulated, sitting at 21V so I suspect one of the regs. I had some spares but they've been misplaced since the last fix I did to it.

Casualties:
1 x Yaesu FT-8900R (no crowbar circuit protection on this P/S). Little diode gone inside the radio so hopefully will be an easy fix... I hope... D1042 a P6KA18 transient voltage suppressor. Someone mention it's just a fancy name for a 15-16V zener.

1 x D3800 P/S

Near Misses:
FT991 - funny enough it powered down, I got the output off the radio quickly... massive panic set in... reconnected it to a battery and it powered up like nothing had happened. Phew!

Moral of the story - install protection on the P/S output... aannnnndd don't leave croc clips plugged in!!!! :D }:[
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VK6AKT
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Re: DSE D-3800 P/S

Post by VK6AKT »

After you fix your supply you need to put something like this circuit between the power supply and the rig .
I only use the over voltage part of this circuit on my D-3800 supply.

Cheers
Ken
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Reverse Polarity and Over Voltage Circuit.docx
Over voltage Protection
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Re: DSE D-3800 P/S

Post by VK7HH »

Thanks Ken,
Yes a right pain.

Hayden
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VK2CSW
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Re: DSE D-3800 P/S

Post by VK2CSW »

Thanks for that Ken.

I'll be assembling one as soon as the weather allows me back into the 'man cave'.

Cheers
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VK6AKT
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Re: DSE D-3800 P/S

Post by VK6AKT »

When you fix your supply I would suggest that you place a resistor (SOT) across TR7 so that the fan runs very slow all the time.
This stops the annoying fan from coming on at full speed when you only have a receiver running.

Cheers
Ken
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D3800 power supply diagram.pdf
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Re: DSE D-3800 P/S

Post by VK7HH »

The amount of DX I've probably missed because of that fan.... :D

I'm going to get a few 2N3055's today.. see which one has blown.

Regards
Hayden
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VK3MH
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Re: DSE D-3800 P/S

Post by VK3MH »

I made a video on repairing one of these power supplies.

https://www.youtube.com/watch?v=plA_8Erz3R4&t=861s

Brendan VK3MH
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VK3ZAZ
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Re: DSE D-3800 P/S

Post by VK3ZAZ »

put a 17 volt idiot diode across output
even old cbs have the $1.50 avalanche device acts as a crowbar
Tread your own path :om:
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VK2LK
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Re: DSE D-3800 P/S

Post by VK2LK »

Close shave on the FT-991!! That was some serious good luck!
Matt, VK2LK
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Re: DSE D-3800 P/S

Post by VK7HH »

VK2LK wrote:Close shave on the FT-991!! That was some serious good luck!
Maybe they are built better than we thought - although I'm pretty sure the 8900 took one for the collective Yaesu team :lol:
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