[Collins] 30S-1 problem

[Gerald]

On Thu, 2006-01-26 at 16:25 +0100, HENRY LEWIS wrote:
> Help please!  Recently when operating with my 30S-1, on releasing the PTT
> the amplifier hangs in transmit mode for a further 1-5 seconds.  This makes
> it unusable, especially in pileups.  The problem is definitely with the
> amplifier and not the exciter, as shorting the relay input on the back panel
> produces the same effect.
> 
> Looking at the circuit, it seems to me that maybe relay K101 is actually
> sticking, or perhaps it could be held on by a leaking C212.  I can't see any
> other potential reason.
> 
> Has anyone else experienced this?  I would appreciate some advice.
> 
> Henry - G3GIQ
> 
Relays can stick. Capacitors can leak.

To check and trace, check the voltage on TB103 pin 2. That's switched by
K101 to run K205, the other RF relay. If that voltage hangs high, then
K101 is staying long. Then check the voltage at J203 or TB103 pin 4.
That voltage should rise rapidly when the control is opened. Make that
check with the cable disconnected from J203 to isolate the cable and the
exciter. Besides C212, C135 could be leaking, though both should be disk
ceramics, I'd think. Without a diode across K101 coil to gather
inductive kick, there can be a significant voltage rise on circuit
opening to overstress capacitors or a solid state switch.

As an aside, if the filter capacitor for the screen supply is increased
from 50 mf to 350 mf, there will be a lot better punch on CW and SSB.

-- 
73, Jerry, K0CQ, Technical Advisor to the CRA
All content copyright Dr. Gerald N. Johnson, electrical engineer