Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thread

[laatsch55]

Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre

I don't see a junction for R10, R15. Bias trans is good on that channel. Voltage referenced from chassis ground on each end of R15, R10 is .o22 volts DC., + dc.

 

[laatsch55]

Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre

Found the junction of R10, R15. .022 volts DC. We're down to 22MV offset, don't know what happened but regulator still getting warm. I'm still on the DIM BULB TESTER, I only have 85 volts DC rail voltage. Is that driving the regulator batty??

 

[laatsch55]

Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre

Going to bed Joe. Got an early one tomorrow. BTW, my thread at AK just went past 1012 views. Pretty interested crowd over there.

 

[Gepetto]

Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre

Hi Lee, are you getting both +85 and -85V on the main rails? If so, I would guess that it is the insertion of your dim bulb that is holding the rails from attaining their full potential voltage.

How warm is warm Lee. Too hot to touch or just warm? The one I have installed in mine is slightly warm but I do not have the protection relays wired to them. Have you tried disconnecting the protection relays to see if removal of that load causes the regulator transistor to cool down. The regulator won't mind 85V at all Lee, mine is running off of 78V in the PL400.

 

[laatsch55]

Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre

Ok , not to hot to touch, but seems warmer than should be. I'll try it with the relays unsolderted and dim bulb out of circuit.

 

[Gepetto]

Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre

Hi Lee, the negative regulator is the second regulator in that same section of the board. You can see it denoted on the schematics as -20V on sheet 3. You can measure it on the large 12K 2W resistor R80. One end should be about -85V and the other end should measure about -20V

 

[laatsch55]

Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre

Taking the relays out cured the hot, just over warm now. I must have som cold solder joints, moving the board around makes the bias jump from .112 to .650.

 

[laatsch55]

Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre

DC offset, Left 21MV, solid. Right 16MV, also like a rock.

 

[laatsch55]

Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre

Could loose fitting output sockets make the bias jump like that too??

 

[Gepetto]

Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre

Yes, if you have marginal transistor sockets all bets are off Lee on obtaining a steady bias.

 

[laatsch55]

Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre

Makes sense, if the load varies, jez. Ok, some tabs are loose, I'll resolder the hookup wires to eliminate that. Then time to load it and feed it some waveforms.

 

[Gepetto]

Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre

You should measure how much those relay boards actually draw Lee. Remember that the regulator you attached to comes all the way down from 100V to 20V so there is normally 80V across the MJE15028. For every 10 mA of relay board load current, you dissipate 0.8W in that transistor.

 

[laatsch55]

Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre

You should measure how much those relay boards actually draw Lee. Remember that the regulator you attached to comes all the way down from 100V to 20V so there is normally 80V across the MJE15028. For every 10 mA of relay board load current, you dissipate 0.8W in that transistor.

OHHHHHHH........... I shall check current. Current starts at .24Ma and drops over time to .06Ma. Checked resistance between ground wire on PCB board and unsoldered + wire.
satrted at 410K ohms, dropping to 70K ohm. out of circuit these relays are only 2K ohm. HMMMMMM...........

 

[Gepetto]

Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre

If the relay coil is a 2K ohm coil as you indicate, each relay will draw 10 mA when actuated for a total of 20+ mA. You will be dissipating 1.6W in that pass transistor which is why you see it warming up considerably. You can put a heatsink under that transistor to help it along. I will send you a picture of the type you should use.

 

[laatsch55]

Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre

Obviously i have a grounding issue, just not sure what KIND of grounding issue.

 

[laatsch55]

Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre

After unsoldering the gound lead for the relays I'm still showing 56K resistance. I believe I have a solder error on the in/out amp wires somewhere. I had to solder blind and upside down the way i put them in. Not the smartest thing I've done. I'll unsolder the amp output wires and see what I have then.

 

[laatsch55]

Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre

If the relay coil is a 2K ohm coil as you indicate, each relay will draw 10 mA when actuated for a total of 20+ mA. You will be dissipating 1.6W in that pass transistor which is why you see it warming up considerably. You can put a heatsink under that transistor to help it along. I will send you a picture of the type you should use.

I have a lot of TO-220 standup heatsinks, could I stand it up??

 

[Gepetto]

Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre

Something like Mouser # 532-504102B00 placed under the TO-220 device

 

[laatsch55]

Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre

Out of circuit hooked up to my bench power supply, at 20 volts with my Fluke 179 in series with + line , upon actuation .45 MA, after cap charge on the relay board, settles down to .08MA.

 

[Gepetto]

Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre

That is without the relay clicked in though Lee. If the relay coil is 2K then you will pick up another 10mA once the relay picks.