thanks for the explanation. I looked at a few other amplifier schematics and you are correct, they seem to all use a bi-polar cap, what confused me is most use a film capacitor, which by nature is bi-polar. I think in this design, the electrolytic is used strictly because of space restrictions. Luckily I had a bi-polar sitting around, so I installed that in place of the one I ordered. I will start with some testing on the protection board, before placing it into full-time use.
Has anyone built and used this protection circuit in a build? I build one (only substitution on BOM is MPS42/92 for the BC546/556 - reversed orientation on board), but when I power up it seems to be working in the opposite of what I think should be normal operation - no delay coming on and about a 2-3 second delay turning off. The other issue is I've tried to induce a DC to create a fault condition - nothing happens??? I have tried with DC power voltage to the board of 12-30V and inducing DC on the output from 1.5-9.5Vdc. I get no disconnect from the input to outputs on the board and no fault indicator LED lights.
Any insight on what might be the issue.
Any insight on what might be the issue.
Attachments
So I guess this means no one has made this protection board and got it working? I replaced the substituted A42/A92 for the spec'd 546/5556 and continues to come on immediately, delayed shut off and has not trigger to disconnect either connection to the speaker and the LED does not light. Would appreciate some assistance, anything to try, since I went to the trouble of ordering boards and have a build I was planning these speaker protection. for.
TIA!
TIA!
Speaker Protection is working!!
Unsure if I had a bad solder joint, or if it was all from a faulty LED, but after re-working the solder connections on most of the board and replacing the LED - the protection board is working on my test bench. I have tested with supply voltage of 12-31vDC, while introducing DC on the outputs of 1.5-9.5vDC and it works without any issues. Will take some time to re-work the wiring in my amplifier I had these planned for, I put in other protection boards while I was working through these issues.
Unsure if I had a bad solder joint, or if it was all from a faulty LED, but after re-working the solder connections on most of the board and replacing the LED - the protection board is working on my test bench. I have tested with supply voltage of 12-31vDC, while introducing DC on the outputs of 1.5-9.5vDC and it works without any issues. Will take some time to re-work the wiring in my amplifier I had these planned for, I put in other protection boards while I was working through these issues.
There’s no link, it is part of this thread, the schematic and gerbers are available in Post #121 if you need them.
Me too in India and keen to build this. Im actually looking for something that includes the speaker protection.
Ping me I have some local contacts who deliver in a week and their prices are on par with JLPCB. So no customs duty.
Im in Bangalore. But my PCB guy is in Pune. And one guy is in Gujarat.
@bullittstang I'm going to put together a pair of speaker protection boards and use them on another project. Glad to hear at least one other person has made 'em and they work 
@intakto I believe there is a pretty barebones parts list in the project files but it'll just have values IIRC.
Here are the parts I ordered from mouser for the protect board:
https://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=81a9380f94
I may have ordered extras of a few things in there. Can't remember exactly. Everything works great tho. Super happy with it.
I used a different PSU so can't help there. I reckon there would something with the values needed in the build files.
Here are the parts I ordered from mouser for the protect board:
https://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=81a9380f94
I may have ordered extras of a few things in there. Can't remember exactly. Everything works great tho. Super happy with it.
I used a different PSU so can't help there. I reckon there would something with the values needed in the build files.
Hey thanks,
This list might be of use to someone.
This list might be of use to someone.
| Name | Designator | Footprint | Quantity | Manufacturer Part |
| bipolar 10uf | C1 | E2,5-7 | 1 | UVP1H100MED |
| 1N4148 | D1,D2,D3,D4 | DO41-7.6 | 4 | 1N4148-DIO |
| TVS Diodes | D5 | P2-15 | 1 | P6KE200A |
| LED5MM | LED1 | LED5MM | 1 | Fault indication LED |
| BC546B | Q1,Q3 | TO92-EBC | 2 | BC546B |
| BC556A | Q2,Q4,Q5 | TO92-EBC | 3 | BC556A |
| IRFB3607 | Q6,Q7 | TO220BV | 2 | IRFB3607 |
| 100k | R1,R5 | 6,3-2,3 mm | 2 | |
| 22k | R2 | 6,3-2,3 mm | 1 | |
| 22k | R3,R4 | 6,3-2,3 mm | 2 | |
| 220k | R6,R8 | 6,3-2,3 mm | 2 | |
| 8k1 | R7 | 6,3-2,3 mm | 1 | |
| 3k | R9 | 6,3-2,3 mm | 1 | |
| TLP3906 | U$1 | SO-6 | 1 | alternative APV1121S |
| 22-27-2021-02 | J4 | 6410-02 | 1 | molex connector |
For the psu i garhered this.
As far as snubber networks go neurochrome notes that it is an exercise in futility as it makes not impact on performance. Most of the designs use 1 ohm but in the rectification and snubbers article, 10 ohms was used so it was also highlighted that exact values are not critical. For 150nf let's say a 6.8ohm resistor can be used. I am starting from 0 on this so i have no left over psu or anything
As far as snubber networks go neurochrome notes that it is an exercise in futility as it makes not impact on performance. Most of the designs use 1 ohm but in the rectification and snubbers article, 10 ohms was used so it was also highlighted that exact values are not critical. For 150nf let's say a 6.8ohm resistor can be used. I am starting from 0 on this so i have no left over psu or anything