That rust converter *Duro/Permatex Extend, Benjamin-Moore M82-00, and others) is a polyester which penetrates and encapsulated the corroded area so that oxygen can not reach it. I buy it by the quart for other projects. It turns black upon cure, and can then be top-coated or left alone.
Any paint that is thinned will also wick into the pitting and seal it. Find a matching enamel in a silver/bronze color which generally matches and thin it , then dab it onto the pitted areas to seal the surface and somewhat mimmic the color. Rust-O-Leum will also work, but will need to be thinned. It is also an enamel. You can also get a variety of model paints (like Testors or Revell) and mix your own color between silver, gold, yellow, green and gray to match.
If you really want the protection of the original finish you can try to find zinc chromate primer. It is widely used in aviation, and used to be sold by Moeller, Tempo, DuPont, and probably many others, like this: http://www.amazon.com/Moeller-025421-Yellow-Chromate-Primer/dp/B001F0O0ZU. It would also have to be thinned.
Any paint that is thinned will also wick into the pitting and seal it. Find a matching enamel in a silver/bronze color which generally matches and thin it , then dab it onto the pitted areas to seal the surface and somewhat mimmic the color. Rust-O-Leum will also work, but will need to be thinned. It is also an enamel. You can also get a variety of model paints (like Testors or Revell) and mix your own color between silver, gold, yellow, green and gray to match.
If you really want the protection of the original finish you can try to find zinc chromate primer. It is widely used in aviation, and used to be sold by Moeller, Tempo, DuPont, and probably many others, like this: http://www.amazon.com/Moeller-025421-Yellow-Chromate-Primer/dp/B001F0O0ZU. It would also have to be thinned.
Great thanks for the advice - lots of options!
I've hit another problem! I got the caps I was waiting for today. I finished the power supply board, turned it on and the relay clicked. So I was testing the voltages and I accidently touched two of the pins together and the relay clicked off. I think it was 14 and 15. Now the voltages at the top of the board are all wrong.
15 is -1v (should be -19v)
14 is -5.3v (should be -51.5v)
13 is -0.6v (should be -13.5v)
I tested the voltages on the transistors. Q7 is OK. Q2 is wrong. The voltage on the collector is correct (-63v) but the emitter (-5.8v) and base (-6.4v) are too low. So I took the transistor out and tested it, but it tests okay. All the voltages on Q6 are way too low, so I tested that too but it's fine. The voltages on Q4 are also all too low.
How can I figure out what's causing the problem? I don't want to desolder everything. I'm so annoyed I didn't tape the ends of the DMM!
I've hit another problem! I got the caps I was waiting for today. I finished the power supply board, turned it on and the relay clicked. So I was testing the voltages and I accidently touched two of the pins together and the relay clicked off. I think it was 14 and 15. Now the voltages at the top of the board are all wrong.
15 is -1v (should be -19v)
14 is -5.3v (should be -51.5v)
13 is -0.6v (should be -13.5v)
I tested the voltages on the transistors. Q7 is OK. Q2 is wrong. The voltage on the collector is correct (-63v) but the emitter (-5.8v) and base (-6.4v) are too low. So I took the transistor out and tested it, but it tests okay. All the voltages on Q6 are way too low, so I tested that too but it's fine. The voltages on Q4 are also all too low.
How can I figure out what's causing the problem? I don't want to desolder everything. I'm so annoyed I didn't tape the ends of the DMM!
It was ZD2! Thank you! Luckily I had some spares.
2nd attempt to test the voltages - I was super careful this time. Nearly all look okay I think - they match the circuit diagram or are slightly lower, except Q9 and Q10. On these, the base and emitters are correct, but the collector is 19.6v and it should be 16.5v, so nearly 20% over (and I'm using DBT). Everything else looks okay though and the relay clicks on.
2nd attempt to test the voltages - I was super careful this time. Nearly all look okay I think - they match the circuit diagram or are slightly lower, except Q9 and Q10. On these, the base and emitters are correct, but the collector is 19.6v and it should be 16.5v, so nearly 20% over (and I'm using DBT). Everything else looks okay though and the relay clicks on.
tsd71
RIP Tom Petty
What are you getting on the pins? 2-3-4-5-6-7-8-9-10-11-13-14-15?
Hi tsd71 - the voltages are:
2 - 6.2v (5.4)
3 - 6.2v (5.4)
4 - 12.9v (13.5)
5 - 12.9v (13.5)
6 - 47.9v
7 - 47.9v
8 - 34.0v
9 - 34.0v
10 - 34.0v
11 - 26.4v (28)
12 - 0v
13 - -13.4v (-13.5)
14 - -51.7v (-51.5)
15 - -19.0v (-19)
And for Q9 and Q10 which seem a bit high:
Q9
E - 6.3v (5.4)
C - 19.6v (16.5)
B - 6.5v (6)
Q10
E - 6.5v (5.4)
C - 19.6v (16.5)
B - 5.7v (6.1)
On Q10, the voltage on the emitter is higher than the base.
2 - 6.2v (5.4)
3 - 6.2v (5.4)
4 - 12.9v (13.5)
5 - 12.9v (13.5)
6 - 47.9v
7 - 47.9v
8 - 34.0v
9 - 34.0v
10 - 34.0v
11 - 26.4v (28)
12 - 0v
13 - -13.4v (-13.5)
14 - -51.7v (-51.5)
15 - -19.0v (-19)
And for Q9 and Q10 which seem a bit high:
Q9
E - 6.3v (5.4)
C - 19.6v (16.5)
B - 6.5v (6)
Q10
E - 6.5v (5.4)
C - 19.6v (16.5)
B - 5.7v (6.1)
On Q10, the voltage on the emitter is higher than the base.
Ok here are the voltages on house power:
2 - 6.3v (5.4)
3 - 6.3v (5.4)
4 - 13.1v (13.5)
5 - 13.1v (13.5)
6 - 48.8v
7 - 48.8v
8 - 34.8v
9 - 34.8v
10 - 34.8v
11 - 27v (28)
12 - 0v
13 - -13.6v (-13.5)
14 - -52.3v (-51.5)
15 - -19.3v (-19)
Q9
E - 5.9v (5.4)
C - 21.5v (16.5)
B - 6.2v (6)
Q10
E - 6.3v (5.4)
C - 21.5v (16.5)
B - 5.2v (6.1)
The collectors on Q10 and Q9 are 25% higher than they should be.
2 - 6.3v (5.4)
3 - 6.3v (5.4)
4 - 13.1v (13.5)
5 - 13.1v (13.5)
6 - 48.8v
7 - 48.8v
8 - 34.8v
9 - 34.8v
10 - 34.8v
11 - 27v (28)
12 - 0v
13 - -13.6v (-13.5)
14 - -52.3v (-51.5)
15 - -19.3v (-19)
Q9
E - 5.9v (5.4)
C - 21.5v (16.5)
B - 6.2v (6)
Q10
E - 6.3v (5.4)
C - 21.5v (16.5)
B - 5.2v (6.1)
The collectors on Q10 and Q9 are 25% higher than they should be.
Sorry to hear, one more time through the mill. Have you got your retractable-spring lead grabbers yet?
Q10/9 form a darlington composite, series pass linear regulator, q10 base is derived from a voltage divider off of the D11 zener reference. q10 base should be one diode drop above its emitter voltage, in order for it to conduct. check pinout/measure/change q10, should be a ksc945c(ECB).2sc869 is( bce). could also use ksc1815,ksc1845 if that is all you have.
The heatsinks on the power board are pretty warm, but not really hot. Not sure if it's related but having trouble setting the idle bias to 20mv on VR4. Protection relay clicks off at about 5mv. R20 was difficult to remove the leg! It tests okay - exactly 100. I'm using 470uF 100v in C12 and C13. I'm using 100W bulb by the way, forgot to say earlier.
I don't know what retractable spring lead grabbers are! I'm using a KSC2383 which is ECB. I've definitely get the leads in the right place. And I've taken it out to test it and it's okay. I could try a KSC945, I need to order one. How do I know how much one diode drop is? I wonder if I put the zener diodes in the wrong places? I put the 13v 1N5243 in D12 and 14v 1N5244 in D11.
tsd71
RIP Tom Petty
Mini Grabbers, no affiliation:
http://www.ebay.com/itm/111533552997?_trksid=p2060353.m2749.l2649&ssPageName=STRK:MEBIDX:IT
You want a bjt with the highest gain, that is because it will load the reference the least, thus better load regulation. But in this case, it really does not matter, any of the suggested replacements will work as long as the pinouts are installed correctly.
For a silicon junction, usually 0.6-0.7V, so for an npn to turn on, the base must be 0.6-0.7V above emitter
Q9
E - 5.9v (5.4)
C - 21.5v (16.5)
B - 6.2v (6) base is only 0.3V above emitter, this is a problem. Note, should be loaded with at least one lamp beaning turned on, so that some current is passing through Q9 C-E to the load.
Q10
E - 6.3v (5.4)
C - 21.5v (16.5)
B - 5.2v (6.1) the base voltage is below the emitter voltage, this is wrong, the b-e junction is in reverse bias = no conduction from collector to emitter.