SB-230 (8873) troubleshooting

[Larry Gauthier]

GT:

A few things to check: (with all appropriate cautions about High Voltages
and the interlocks and etc, right???)

Please forgive any assumptions I make during this trouble-shooting
routine... I don't like taking things for granted (I worked at Heath for too
long... and we often saw 5 year old rigs come in for service that could
_never_ have worked properly!)

FIRST QUESTION:
This thing worked properly once, right?????

IN STANDBY MODE
Receive antenna signals get through the amp (the relay circuit works in
receive mode)?
Panel lights turn on?
Delay lamp goes out after ~2 minutes?
HV meter reading around 2.2kv?
0 (zero) plate and grid current when in receive mode?
Transfer relay operates when the rear-panel relay pin is grounded (not in
exciter mode)?
Rear-panel grid fuse (3/4 amp) is not blown?

INTRANSMIT MODE (with no RF drive)
Relay operates?
Grip current stays at 0
Plate current climbs _slightly_ (small meter movement)?

IN TRANSMIT MODE (with some RF drive)
Grip current climbs to some value?
SWR from _rig_ to _amp_ is low (less than 1.5:1)?
Plate current climbs proportional to drive?
Plate cap tunes/dips?
Output power appears on relative power meter or wattmeter?

TESTING THE 8873 (TURN OFF THE AMP, unplug it, allow HV meter reading to
decay to 0 volts, open amp, short B+ to ground woth a screwdriver for safety
just in case)
Is the tube "warm" (the filament was getting hot)?
B+ on the tube? (Assuming you cannot read 2.2kv with your VOM, measure for
continuity from the tube to the B+ line in the power supply to make sure
that B+ is reaching the tube.)
At this point, it looks like the tube may have failed (prayer is appropriate
at this time... ;-)
Remove the tube from the socket - being careful to wiggle the tube gently
while pulling on the tube, since these plastic tube sockets are known to
crack.
Using the ohmmeter, measure for open circuits between the cathode (pins
1,2,3,8,9,10), grid (pins 4,7,11), filament (pins 5, 6), and plate.
Using the ohmmeter, measure for filament continuity (pins 5 and 6, about .8
ohms).

Hope this helps. My apologies if my questions treated you like an idiot - I
take no chances! Let me know what you find, we can work from here with some
other tests. (filament supply, zener diode, chokes, caps, etc)

-larry
wb8bgo

-----Original Message-----
From: G.T. Awalt <kk5vr at ARN.NET>
To: HEATH at LISTSERV.TEMPE.GOV <HEATH at LISTSERV.TEMPE.GOV>
Date: Tuesday, April 06, 1999 11:29 AM
Subject: SB-230 (8873)


>Hey folks;
>I have a SB-230. It appears to work OK with one exception, no output.
>Is there a way to check (with a VOM, it's all I have) for problems? I
>have no info/manual on the unit. How can I check that high dollar tube
>with what I have.
>Thanks for your time...
>GT  kk5vr
>
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