Parts Order

Sorry I didn't see your post because I left for HC8 the day before.

The hum was probably from low line voltage, as the regulators drop out
of regulation at around 106V. We run our 930s on 240 or 220 so we can
use the switch, and use a 240V surge protector because we're at the very
end of a lousy line.

I'm assuming you have S/N>310XXXX. The zap was probably the 22V
regulator transistor on the PS heat sink, which takes with it the
emitter follow that drives it and it's zener. It's a lousy circuit, but
you can use NTE equivalents and get good results. Be sure the pass
transistor screw is tight. Unsolder the fat leads on the PS board if
you need to remove it. You should check first to see if the 22V is
coming out of the small transistor emitter follower on the board, in
which case you can leave it alone. It's fried if the voltage is either
zero or 31V.

The PS is the weak spot, and the part that feeds the digital board and
the signal board is the worst. The 28.5V section that uses the big TO3s
to feed the amp is better, but some folks have had bad luck and zapped
final transistors. To get the PS heat sink off you have to take out the
screw that holds the diode quad and disconnect the lugs on the back of
the TO3 transistors. When you are done the little white wire to the fan
will have broken and should be resoldered.

GL OM, we have five 930s and all are now 48+ hour reliable. But it's
been a battle!

73 de Dave, W6NL/HC8L

Return-Path: <k8rf@cinci.rr.com>
Date: Tue, 05 Dec 2000 19:04:06 +0000
From: "Dan Flaig, K8RF" <k8rf@cinci.rr.com>
X-Accept-Language: en
To: Geoff Howard <ghoward@kent.edu>
Subject: Re: 930 Question
References: <3.0.32.20001205113900.018f6500@pop.kent.edu>

G-
I've had a 930 Power Supply go out before, and also fixed one of W8TKs 930's
that blew its supply, I am trying to remember all the details abt what goes
out... potentially quite a few things, also if D7 has to be changed the power
supply voltage will change slightly as this diode sets the main power supply
voltage level, this means you should align all the VCO/BFO oscillators with a
Frequency Counter....fun,fun

It just depends how high the voltage spiked before the fuse blew, it is
possible it just blew a few things in the power supply, but unlikely.

The power supply proper has its two main series pass transistors ( Q1 & Q2 -
2N5885 in TO-3 Cases) are mounted on the power supply heatsink along with a
smaller transistor (Q3 - 2SD843) in a TO220 case, They all three might be
toast, but no telling might just be smaller one. All three are mounted with
heat sink compound

The power supply PC Board has several transistors and diodes, probably D7( a
29.2 volt zener) and Q1 are gone and maybe some more stuff, I'd buy all the
Diodes and transistors for the Power Supply PCB just in case.

Also the Final RF AMP has a 'overvoltage protection diode', D1 a 50 Volt
Zener, it is shorted out I'm sure...if you are carefull the diode can
actually be removed from the Final PC Board without tearing the final amp
assy out of the rig (LOTs of work!!!), or as a 9Q5 Jury rig you can snip the
diode in half and just leave it there and rig will work... but if the power
supply fails agn without the diode there you run the risk of smoking the
final RF transistors.

Also, if I remember, there might be another Zener somewhere else that goes
out also, I will try and jog my memory.

The S-meter problem could just be a blown diode D245 but also IC7 (the Op amp
that drives meter) might be blown.

The fact you have no display means there are problems with voltage gg to
digital board, the main 28 volt supply gets knocked down to abt 10 volts and
18 volts by Zeners D6, D7 and D8 (along with R7 - 22 Ohm 2 Watts, R8 and R9 -
82 Ohms at 2 watts, R10 - 33 Ohms at 2 watts....These parts are chassis
mounted (near the Final RF amp if I recall)
Also on the digital board itself the 5 and 12 volt regulators could also be
bad.



There might even be some other stuff thats blown , hard to guess

As far as tools, you need a GOOD soldering Iron and Solder Wick, the PC
Boards have plated through holes that can be damaged.


If you do try and fix it youself, disconnent all the 28 volt line connections
from the power supply gg to other parts of the radio: the big red wire gg to
Final RF amp, Connector #1 on the digital board, connector #2 on AT Unit, and
connector #29 on the Main Signal PC Board.

So you can see this most likely is no small job, I would probably recommend
that you bring the Rig back stateside and I'll fix it for you!

G-
Also the two resistors R4 and R5 (2.2 Ohms 1/2 watt) on Power Supply PC
Board, also maybe R1 (also a 2.2 Ohm AT 1/2 w) could be toast
73
Dan