Don't give up - it's starting to work. We just have to find the hiccup - and when you have it seems to work then cuts out, I'm looking at obvious stuff, onto the more exotic - these radios - although fun, are also a drain on ones' resources. So this is a special one and I'd hate to keep having you to go thru all these different approaches like you would if you took a shotgun to it - hence Shotgun approach...But much of what we've looked thru and checked are ok from it's own standpoint.
So when you have time to spend on it, it will need to have that event happen and use a tester with hook on the leads so you can probe a transistor leg and as you key up and test - when it quits - we need to see if the transistor as part of the chain - goes dead. If it does - its a power supply or toggle issue, if it still holds power but doesn't send - you move onto the next part up the chain...
Considering the problem that Robalos' TRC-453 had - if the IF of one section quits while you're in transmit - this can cause the "quit" syndrome. Doesn't mean you'll lose the RED TX light - just that it failed while you talked and the radios' PLL thinks it's ok, but it's not sending.
Now, we also removed the LIMITER transistor before and it still did this , so I'm not leaning on TR28 as being even part of the problem - just wanted to make sure it was not pulling power. IT would affect the Limiter - even before TR28 - but TP5 is still connected to that portion of the IF - your Audio side of it - if you have a Frequency counter - put it on there (TP5) - a scope is better but frequency counter would show if that section is still working when it drops out ... nothing on the counter or it would shift to 17MHz because it lost the lock on the 10.6~10.7 MHz audio side meaning that section is not locking.
The same could be said for the PLL's IF section - if that were to lose lock - the PLL would switch to OOL (Out OF Lock) but it CANNOT change the TX LIGHT - that is locked in by your Mic PTT - it can only keep the light off, when the PLL thinks it's out of lock in the RX MODE - but when it does go out of lock - IN TRANSMIT - it can't change the status, but it can keep the radio from transmitting - by not providing any IF to the TX Mixer so it just sits there...
That issue is part of the PLL's and can be a voltage problem.
