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CR-1020: After recap stuck in protection SOLVED

Johnny_Law

Johnny_Law

o.O
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Edit: Solved, see post #82. If your CR-1020 is stuck in protection, and the FM tuner dial is stuck to the left of center, check TR712 and TR715 on your Power Supply board!

I just recapped my CR-1020 (electrolytic board, power supply / protection board, main amp boards) and now my DBT burns bright and it won't come out of protection. Neither do any lights illuminate at all.

(However, and this is odd, but if I unplug the power supply board from the elecrolytic board, the LEDs turn on and the light bulbs show very dim current, and the DBT while still very bright is slightly less bright.)

I measured O-E on both amp boards, very low, no DC issues.

Since it isn't a shorted output transistor, back to the power supply. I started with the transformer ... and, uh, I don't think this is right.

Between Blue wires into the power supply board, I am measuring about 2.75VAC, manual seems to spec 17.2VAC (hard to read)?

Between either AC (red) to CT (black) into the Electrolytic board, I am measuring about 5.75VAC, manual seems to spec 36.0VAC.

I had a variety of loose connections which I re-soldered, and verified all wires between boards are intact in the correct spots and soldered. All new caps are in correctly. I also replaced TR712 and TR715 on the power supply board with TIP31A. They are in correctly (hard to mess it up thanks to the heat sinks).

I'm a bit flummoxed, it was operational before the re-cap. Would love any thoughts you all may have.

Thanks,
Ryan
 
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Since everyone loves pictures, here are a couple I snapped during the re-cap.

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This little guy came off but I replaced it with a new wire... to E3 on the electrolytic board

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You will see reduced voltage out of the transformer while on the dim bulb. Maybe you already know, but I thought I would point it out. Also, the polarity mark for one of the caps on the e-Cap board is WRONG. If you aren't already aware of this, that might be your problem. That happened to me on my first 1020.
 
DRecovery said:
You will see reduced voltage out of the transformer while on the dim bulb. Maybe you already know, but I thought I would point it out. Also, the polarity mark for one of the caps on the e-Cap board is WRONG. If you aren't already aware of this, that might be your problem. That happened to me on my first 1020.
Click to expand...

Thanks! Hmm, but it should still come out of protection on the DBT though, correct?

And thanks for the tip, yes C805 or C806 (can't remember which), I read all about it in previous re-capping threads so I made extra sure it went in correctly.
 
If the dim bulb is bright, then you are dropping most of your voltage across the bulb and there is not much left over for the receiver to run on. It's doubtful it would come out of protection under those circumstances. To know for sure, you could measure the voltage to the receiver. I don't remember if the CR-1020 has accessory outlets (Switched / Unswitched) in the back or not, but that's a convenient place to do measure the line voltage to the receiver if your dimbulb tester doesn't have a spare outlet.
 
Yep, I measured it at 120VAC to confirm I was getting the full boat. So it was seeing 120VAC and the bulb was bright. I'll measure it again, though.
 
DRecovery said:
If the dim bulb is bright, then you are dropping most of your voltage across the bulb and there is not much left over for the receiver to run on. It's doubtful it would come out of protection under those circumstances. To know for sure, you could measure the voltage to the receiver. I don't remember if the CR-1020 has accessory outlets (Switched / Unswitched) in the back or not, but that's a convenient place to do measure the line voltage to the receiver if your dimbulb tester doesn't have a spare outlet.
Click to expand...

Well, nevermind! I just re-measured and I'm only getting about 19.5VAC through the DBT. So only about 10% of what I should be getting.

So I guess the DBT is doing its job and dropping the voltage because of excessive current draw from the 1020. Which, I think, makes sense of the transformer's output voltages. But also means I have a short somewhere, so it seems.

Title of thread edited accordingly.
 
Partially solved - the bright bulb wound up being the result of my TR608 replacement KSC1845s going in backwards - the datasheet confused me I guess, not the first time it's come up.

Now the DBT dims down and the lights come on, but it's still stuck in protection. It doesn't even come out of protection with the amp fuses pulled, so I suspect an issue on the power supply board itself.
 
avionic said:
T-shoot the power source for the protect circuit/ relay. Somewhere on this board.
Click to expand...

Thanks, I was just reading your help in a similar situation here.

FWIW since I took that picture, TR701 and TR705 were replaced with KSC1845 (iirc), and whatever that last original capacitor is was replaced with a new cap.

I measured TR702 in circuit and measured 19.92VDC on both E and B, nothing on C. When I jump E or B to C, protection relay releases. I pulled TR702 (original 2SB544) and confirmed it's operational using the diode test.
 
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avionic said:
Maybe. Maybe not. It could be failing to properly switch under actual circuit load.
Click to expand...

Hmm, I'll test the upstream components of B and E until they meet (from E, R751, D718, R748, R745; from B, R750, TR706) and see if I see anything weird.

(No trace / lead damage or bridges observed, will double check.)

If I can't find any issues on either side, it would seem like the issue would have to be TR702 itself. If so, I've found substitutes for the PNP 2SB544 recommended as KSA992 or KSA1013, I'll see if I have any of either lying around.
 
avionic said:
Is there any residual dried glue around TR702?
Click to expand...

I've been hitting it with 99% isopropyl alcohol on a stiff little brush, can't see any more dried glue although as you're aware these boards are full of it.

So, turns out I've got the same ~19.2-19.8 VDC at C on TR706 that I have at B and E of TR702. Almost like they are connected. Upon testing, there is no direct continuity (no beeeeep on the multimeter).

How the heck could there be close to 20 VDC at TR706 C?!

I replaced TR706 with a KSC1845 I have on hand, no change, still the same ~20 VDC at C. So I put the original 2SC1918 back in.

(Bridging E or B to C on TR706 also causes the protection circuit to disengage.)

I removed R750 and it tested within spec out of circuit (~3.8k).
 
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