I used 27k 25k, 22k, 18k, 17k.
I have only one bench power supply which I used to power the board with 24v.
Testing for DC offset was done with batteries, 9v,3v,1,5v.
27k 25k and 22k gave me the same results. When I used the 3v batteries relay was going on off constantly. Looks like I was on the threshold. with the 18 and 17 k and 3v bat. i could securely switch off the relays.
None of the resistor values switched off the relays when using 1,5v.
When I'll plug the board on the amp, then the bench psu will be free for some more extensive testing. What I'm looking for now is what is the speaker tolerance.For example is it best to keep the threshold at 3,2 or 1,5v?Or higher?
There is a kit in the market that has a threshold of 1v but I believe this is too low.
I have only one bench power supply which I used to power the board with 24v.
Testing for DC offset was done with batteries, 9v,3v,1,5v.
27k 25k and 22k gave me the same results. When I used the 3v batteries relay was going on off constantly. Looks like I was on the threshold. with the 18 and 17 k and 3v bat. i could securely switch off the relays.
None of the resistor values switched off the relays when using 1,5v.
When I'll plug the board on the amp, then the bench psu will be free for some more extensive testing. What I'm looking for now is what is the speaker tolerance.For example is it best to keep the threshold at 3,2 or 1,5v?Or higher?
There is a kit in the market that has a threshold of 1v but I believe this is too low.
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Hi,
I have used BC546B transistors instead of the 2SC945, and a MPSA42 instead of the CS9013. I use 2 x 12V DC Omron relays. I tried to use the circuit at 24V DC.
But I'm experiencing strange problems... The flip flop is blinking at a too high frequency, so it's steady on. And the relays are switching almost immediately at power on. Only if I lower the voltage from 24 to about 10 to 16 volts I see the LED blinking ( frequency goes down with lower voltage). And only around 18 Volts the timedelay is about 2 a 3 seconds before the relays switches. Under 17 Volts the relays don't switch anymore. ( thats normal).
Why do i have this behaviour? Is it because of the BC546B's or the MPSA42?
Should I take a larger capacitor for C3 for a longer timedelay? Should I take larger capacitors for the flip flop to lower the frequency?
I have used BC546B transistors instead of the 2SC945, and a MPSA42 instead of the CS9013. I use 2 x 12V DC Omron relays. I tried to use the circuit at 24V DC.
But I'm experiencing strange problems... The flip flop is blinking at a too high frequency, so it's steady on. And the relays are switching almost immediately at power on. Only if I lower the voltage from 24 to about 10 to 16 volts I see the LED blinking ( frequency goes down with lower voltage). And only around 18 Volts the timedelay is about 2 a 3 seconds before the relays switches. Under 17 Volts the relays don't switch anymore. ( thats normal).
Why do i have this behaviour? Is it because of the BC546B's or the MPSA42?
Should I take a larger capacitor for C3 for a longer timedelay? Should I take larger capacitors for the flip flop to lower the frequency?
Except for the relays being different, I have been using two identical boards for 12V and 24V without too much change from the flipflop or the r-c timer.
Changing the value of the flipflop and c3 caps will of course alter the time constants of both. But before you do, please check that everything else is of the right value and that they are where they should be. As I have said above, been using/testing both on 12V and 24V supplies without any problems and so it was not mentioned in the build guide anymore.
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.
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.
You, me, Both.
But $19,- isn't too much anyway, but it would be nice if You guys could split up theese bardsa.
You, me, Both.
But $19,- isn't too much anyway, but it would be nice if You guys could split up theese bardsa.
Yes, 19 USD isnt too much but why wasting the materials...
Maybe we can arrange a swap whit someone who needs only the speaker protection board.
Someone???
Or the best would be if you DIYAUDIO store would offer separate boards???
Thanks for the feedback - we'll definitely see what we can do in the future. If we do it it won't be until we do our next re-order (what's in the store is what's in the store, we can't split stuff up that is in there now).
You're welcome to swap stuff in the swap meet!
Hi Jojo, I finished the speaker protection board, tests correctly, and when hooked up to f5 dc protection cuts in. I have adjusted dc output following nelson's instructions in F5 doc and have very very low, between zero and 5mil much below docs allowable but still the protection cuts in. Would this be in your opinion constructino problem or is protection board not going to work with this amp if DC output is really really zero. Doyou know other people using this board with f5 whom might have a similar problem.
Hi,
Please check the values of R11, R12, R13, C4 and C5. I have tried the speaker protector board on an F5 without any issues so let's consider this as a construction problem at the moment. Kindly check the values you have installed in the board and make sure they are what they should be.
Thanks
Please check the values of R11, R12, R13, C4 and C5. I have tried the speaker protector board on an F5 without any issues so let's consider this as a construction problem at the moment. Kindly check the values you have installed in the board and make sure they are what they should be.
Thanks
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