And on a secondary note:
No one mentions this anymore so I will...
Remember the mA reading you take, the recommended?
I would take a moment of time and research - investigate - the bias readings you make on the Test Point jumpers.
Do this and save yourself some money in replacement Bi-polars later.
You might want to subtract some numbers off of those readings and use those NEW LOWER numbers to set them - it depends on several factors as to the WHY I suggest that - read on if you insist.
(e.g. - if they say 70mA - use 45mA (about 1/2 rated) when you see 50mA use 25mA - if you can no longer replace the Bipolars with new stock ones, think 2/3rds to 3/4 LESS than rated...especially if it's old aged and hasn't been recapped in a while)
Use a dummy load...
Remove test jumper...install the mA meter for taking readings...
If you have these in an SSB radio - turn on the radio and check the mA readings ...set them to 60mA OR LESS
Remove the meter - install the jumper...
In to a dummy load, key up the radio in AM or FM mode for 2 minutes...
Remove the Jumper - install the meter - do this quickly as possible...
Retake your readings...
Note those readings - and realize that as the Final and Driver heat up, they "see" more current to use so their mA readings will change and in some cases rise considerably - to a point that you really need to turn the mA Bias trim down even further...
Change, tweak, or adjust as needed - and more times than not - the readings will show the trim settings are a bit too high and you need to remember that reading change, in rate as well as in amount. Because as things heat up - those readings do too (go up) and it's important that you compensate for that. All of this free advice is to aid you in keeping a customer happy.
Why this step?
Profile - develop a profile of which part / section heats up and DRAINS more current thru it when heated - because you may have to go back someday and tweak that section - Driver or Final - to correct a thermal issue.
Whether its:
Assembly - Hardware is not seated properly, bent flange, Heat sink panel not flat or clean, even - too much heat sink goo and now you have a gap that prevents the quicker transfer of heat from the part to the panel...
Components - Parts age, poor soldering heat stresses components and traces. Environment affects it too - moisture (humidity) dusty (dirt contamination) and temperature in the mobile installs can shorten the life expectancy of a radio.
Previous Repairs - Yes, sadly enough you may have to go back in and fix work done before. This reason alone can be the result of why the radio is in the shop in the first place. Part suppliers change, go out of business and original OEM are no longer available -you or they did what they could now you have to take the ball and run with it.
So while people may scrutinize work - if you keep your ducks in a row - your work won't show back up on your desk, the bosses' desk or on youtube to be ridiculed and scoffed at...Because you did the best you could - now if it burned up and they have to undo what was done and re-do it - let's hope all those hoops you went thru are the steps you took to do the job right.
I get "Dinged" everyday by those that have taken my "placard" of doing research seriously, and testing me - now I get to let you in on some secrets to why I get treated this way...
There are reasons for doing what I do - it's not always easy to describe the Why - because it's experience that has taught me these things - you don't have 30 years to wade thru all those "Teaching moments" I've had - I'm just trying to give you some "Cliff Notes" about them.
Then there will be times they will do it to themselves - we are in a teaching moment here. This shows us we're human. How some will react to a simple failure is one thing, and a lot of people these days are blaming assembly as the main problem with failures - referring to the "Customer is always right" rule. Which means they - the shop boss - is convincing the customer that they know what is best and
tell them to Ignore the warning signs in, on and around the sides of the box that says...
STOP! Read The Instructions First! Your satisfaction is important to us. If you are having problems - Call 1-800-xxx-YYYZ and tell us what you need. Do Not Return Product To The Store!
Ignorance is Bliss - but is 99% of the Law - because if the Manufacturer doesn't realize something's wrong in the box, how are they ever going to be able to make it right?
I've had customers return radios back in the box - with cut leads and blown fuses and scratches everywhere on the case - I have to eat a cost on that - but I too have called those 1-800 numbers to get this POS off my desk and back to the place it came from so they could yell at the Quality control staff - if any...
Back to the Thermal issue...
Remember - some manufactures do not always say what the temperature readings needed to be or the length time into the testing on the bench needs to be taken - before it's considered "warmed up and stable" enough to be tested. You need to skip that and re-create the real world stuff - the environment it will be used in.
AC is nice on a hot day, but does little comfort when it (radio) and the customer are in a position of embarrassment due to your failure to provide that safety margin. Whether it's the hottest day of the year outside or the coldest on record - that radio was purchased with a level of trust - don't blow it by spending time on scruples and back-biting - fix what's wrong for the customers sake - even if it means having to violate the OEM rules and modify the radio to suit the environment it's going into.
So there is a reason for why I do what I do and show how I do it - for the reasons that your life may depend on it someday - especially in extreme weather conditions and you have to travel when it's not recommended - that radio may be the only thing that still works when other devices fail. Not because of you, but because of the environment took out the support towers and power lines feeding them, they're gone.
Sometimes the shine you have gets tarnished, but with a little more effort - the shine can be returned. And Shine is a relative term - for it is not always that, things that glitter are not always gold.
If you're read this far - Congratulate yourself - because instead of having to wade thru 30 years of times past to locate what you need, you got this far from a guy whom' has done things and made the mistakes through the past 30 years, so you don't have to. You've just saved yourself 30 years of time by taking this research to heart.
:+> Andy <+: