[Premium-Rx] Watkins Johnson 8711A Repairs after 10 Years

[Steve Pappin]

Q and A: I bought a WJ-8711A and it has some issues. What should I do?

I just responded to a typical WJ-8711A question and wanted to share this 
with the group. These radios are coming in faster all the time. Why? They 
are end of life. Consider the MTBF which is 10,000 hours at 40 degrees C or 
40,000 Hours at 20 degrees C. After 10 years the radio is well beyond it's 
life cycle. It is not the same as a MIL-STD radio manufactured pre 1985. Why 
so many issues? Compare the 8711A to a fully optioned radio that cost 
$80,000 to manufacture in 1983. They have very little in common. The 8711A 
design criteria was COTS = Commercial Off The Shelf and Planned 
Obsolescence. The US govt runs on different criteria and a different budget. 
We are going to run out of sources for viable parts. Many of the NOS parts 
that come in are compromised. This leads to a very candid Q and A. What can 
we expect?

1) Repair Cost: I need to see it before I can estimate repair costs (please 
read below). Estimate: usually $100.00 to $500.00 depending. If the front 
panel is trashed it could be much more. A new front panel costs 
approximately $4000.00

2) One suggestion: If you are a hobbyist buy an organ donor 8711A in good 
cosmetic shape and use it for parts. That's what many people are doing.

3) The Front Panel is Intermittent: What you are describing sounds like many 
radios that are coming through the shop. Manual gain / Function control / 
Intermittent Front Panel: The thick film encoders lose the wafer welds. The 
wafer shorts to the front panel circuit board and also looses functionality. 
Moving the encoder or circuit board around changes the degree of error and 
fault. Since the encoder is not attached to the front panel by the bushing 
all of the load goes into plastic encoder shaft / plastic housing. The 
plastic welds break and they cannot be repaired reliably. I tried aerospace 
epoxies and JB Weld. They all fail within a few months. The case moves and 
flexes so much. The encoders are disposable.

4) What Else: The other intermittent issues are related to grounds, power 
supply regulation, and loose contacts. All of this ads up over time. The net 
result is flakey operation. That is why DRS suggests replacing entire 
assemblies. The price for an assembly can be the cost of a new radio.

5) Can I repair it? To be honest the answer is, yes, for a while, but there 
will be new failures. The switches will be the next to fail if they aren't 
already failing. Next the optical tuning encoder. All of the low cost 
connectors will become intermittent at some point. The grounds will need to 
be updated. In the end the cost of repair can become so high that many 
people abandon the radio. The US Govt doesn't seem to have a budget so they 
just keep paying to fix them. That however is nearing an end because the 
last complete run of new radios left the production line last year. There 
will be no more new radios. DRS said EOL period.

6) What can I do? The best solutions if you don't have an unlimited budget:
1) Don't use the front panel. Run the radio from the serial interface to 
reduce wear and tear.
2) Buy a parts radio. In the long run this will save you $$$ in repairs
3) Have your spares serviced so that you can swap them in

I can repair these radios but the cost is rising steeply. It's becoming 
harder to find parts and the prices are incredible. I just put in an RFQ for 
encoders. The last time I did there was a 100 Piece minimum. The same is 
true for connectors and many other pieces. Many parts are odd which promotes 
planned obsolescence.

In the past year I have seen a large number of these radios come through the 
shop. That's not so good. I am wondering how long this demand will continue. 
How many 8711A's are out there that need repair? The truth is that many of 
these radios were scrapped because they had crypto options loaded. The plain 
ones that are surplus and needing repair will exceed the budget of most 
hobbyists. That's why many of the surplus 8711A's show up here, get 
repaired, and go to a new owner.

Summary: This radio was simple to manufacture. It is not cheap to repair. 
Those who have repaired them understand. I'm not trying to kill interest in 
this radio but expectations should line up with reality. Consider the parts 
or services that you will need in order to keep this radio running:
1) Install a new RAM / Battery
2) Have the power supply serviced
3) Install optional front panel grounds
4) Clean all of the front panel connectors and check contact tension
5) Replace bad encoders
6) Replace bad switches
7) Replace the front panel if necessary
8) Buy a second radio or spares

Never:
1) Clean the front panel with volatiles which melt plastic or remove the 
printing on contacts / encoders.
2) Handle internal parts without anti-static precautions
3) Up-grade firmware unless you know exactly which model and options you 
have installed

Best Regards,
Steve