Speaker Turn On Delay and DC Protector Board Set (V2)

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#63
WalterW said:
Problems solved!
For 24V with BC546B's I made the following changes:
- R5 from 470 Ohm to 2K7. To lower the voltage of the flip-flop.
- C1 and C2 from 2u2 to 10uF, to lower the frequency some more.
- The RC with R6 and C3 was changed to 1MOhm and 220 uF. Now I have around 4 seconds delay.
- I also changed R8 from 1K to 22KOhm because T6 switches around 7.5 Volts ( I think Vbe + zenervoltage) and in the 24 Volts version it switches immediately cause the voltage is always above 8 Volts on the emitter of T3.
Everyting works fine now, between 20 - 28 volts.
Maybe this is usefull for the European DiY's where BC5xx series is very common.
Click to expand...

I tried to order parts from Digikey.com and mouser.com
The 2SCxxx transistors are no longer available in the USA also.
However I did find the BC546B's readily available on digikey.
I think updating the BOM to substitute the 2SCxx for the BC5xx makes sense for the Euro's and the USA's.
Thanks to you Walter!! Much appreciated. This will be a nice board when finished.

😀
 
#64
I, too, have been pulling at my hair in the search for parts for both pc boards. Thanks nrg2009 for suggesting a replacement for 2SC945. But what about CS9013? I can't find it either.
Would also like help in finding somewhere to purchase C9 and C11. X & Y class? It doesn't compute in any of the suppliers' search windows. What type are they? Polyester, electrolytic?
I'm building ESP's P101 and Rod's instructions and descriptions are explicit just for neophytes like me. I found all the P101 parts in nothing flat.
Please advise about relay voltage. I've ordered a Plitron for the P101 that has 2 spare secondaries of 8 and 13 volts respectively. Therefore, I'm assuming I should buy K1 & K2 at 6volts?
Thanks for listening.
 
#66
Hi, I finished my speaker protector, but the led continues to flash and never closes the relays. Actually, it did close them the second time I powered it up, but won't anymore.

I'm using the 18v toroidal that powers the F5, and 12v relays. Any ideas why it would work intermittently?
 
#68
The F5 will output a larger offset when cold and during warm up.
The speaker relay could be detecting that and refusing to close.

A longer time delay would give the F5 more time for the bias currents to settle.

Once a DC detector is triggered they can take a long time to unlatch and some rely on leakage current to get the trigger voltage down below threshold.
 
#70
nrg,
I don't know.
In simulation, the switch off can be so quick that only tiny amounts of energy get through.

The problem that simulation cannot model is DC.
I have no idea how long the arc across the opening contacts would last.
I have no idea whether the relay would weld in attempting to break the DC.

Here supply rail fuses would help, but many amplifiers do not react well to a single rail fuse breaking.
 
#71
AndrewT said:
The F5 will output a larger offset when cold and during warm up.
The speaker relay could be detecting that and refusing to close.

A longer time delay would give the F5 more time for the bias currents to settle.

Once a DC detector is triggered they can take a long time to unlatch and some rely on leakage current to get the trigger voltage down below threshold.
Click to expand...

How would I extend the time delay?

Also, it blinks at a very high speed. Would that indicate a construction problem?

Thanks for the help.
 
#74
I just checked the voltages on the F5 after working it hard for a couple of hours:

Left channel: 5.96v bias, 3.5mv offset🙂
Right channel: 5.96v bias, 0.0v offset 😀

So I don't know why the speaker protector would have a problem with DC with this one.
 
#75
McQuaide said:
Jojo, any ideas?
Click to expand...

Could you please post the transistors you used? It is not a "picky" circuit, so any reasonable general purpose transistor can be used.

Also, please check your construction, parts orientation, polarity, etc. There could be two possible causes for the circuit not to trigger. One is DC offset, but since you posted very low DC offset readings, then the second one could be that there is not enough voltage build up at C3.

Checking the parts values, one by one usually shows the culprit. It is not a surprise to mistakenly think that a 2.7M is a 270K resistor.
 
#77
JojoD818 said:
Could you please post the transistors you used? It is not a "picky" circuit, so any reasonable general purpose transistor can be used.

Also, please check your construction, parts orientation, polarity, etc. There could be two possible causes for the circuit not to trigger. One is DC offset, but since you posted very low DC offset readings, then the second one could be that there is not enough voltage build up at C3.

Checking the parts values, one by one usually shows the culprit. It is not a surprise to mistakenly think that a 2.7M is a 270K resistor.
Click to expand...

I used this one for T6

MPSA06 Central Semiconductor | Mouser

And these for T1-T5

2N5232A Central Semiconductor | Mouser

I'll check the resistors one more time but I think they are right. I just went over the Mouser BOM I used, and all the right values were ordered.

Sorry for the giant photo...

An externally hosted image should be here but it was not working when we last tested it.
 
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#78
I just rechecked everything, went over the board with a magnifying glass, and tried it again. It trips after 4 seconds or so with nothing connected to it. Still won't close the relays with either of the F5 outputs connected. I monitored DC during power up on each channel, and it's under 10mv.

The F5s are being fed by a Mesmerize buffer which takes 8 seconds or so to engage its relay. So the F5s have nothing on their inputs during power-up. I wonder of this matters?

JohnGeneva above had the same issue, and he said he just built another board, and that one works with his F5.
 
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