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If a dc-fault condition arrises at the amplifier output the dc voltage at R32/C16 will reflect this and it will be either + or - depending on the fault.
A + fault will turn on Q12. This will pull-down the voltage at the base of Q15 and turn it off, draining the charge on C20 via R35 and depriving the opto of current thus disconnecting the speaker.
A - fault will turn on Q13. This drains C20 and pulls the base of Q15 down to turn everything off.
It's not the fanciest circuit, it has some weaknesses and no doubt could be improved by adding more parts but I like it's elegance.
A + fault will turn on Q12. This will pull-down the voltage at the base of Q15 and turn it off, draining the charge on C20 via R35 and depriving the opto of current thus disconnecting the speaker.
A - fault will turn on Q13. This drains C20 and pulls the base of Q15 down to turn everything off.
It's not the fanciest circuit, it has some weaknesses and no doubt could be improved by adding more parts but I like it's elegance.
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Good catch, looks like I had planned for 1k and then later changed my mind and increased it to 4k7 (likely based on simulations) and forgot to remove the first appearance of R35 from the BOM. The as-built value shown in post #604 is 4k7, go with that.
This resistor is there to limit the peak current through Q12 if a dc fault is detected at the output and results in Q12 being turned on hard in order to drain the charge off C20 so that the base of Q15 is pulled low to 'open' the solid state relay. It's likely that 1k would be fine, but 4k7 is better, especially when using higher rail voltages. The circuit achieves a similar function to the one you looked at last year on Bonsai's design.
I'll be interested in your impressions of the TGM8 as compared with your HoneyBadger amplifiers.
This resistor is there to limit the peak current through Q12 if a dc fault is detected at the output and results in Q12 being turned on hard in order to drain the charge off C20 so that the base of Q15 is pulled low to 'open' the solid state relay. It's likely that 1k would be fine, but 4k7 is better, especially when using higher rail voltages. The circuit achieves a similar function to the one you looked at last year on Bonsai's design.
I'll be interested in your impressions of the TGM8 as compared with your HoneyBadger amplifiers.
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Thanks Bigun.
I just started stuffing the TGM8 boards, so it will be a while before they can be compared to the Badger. Also, I had a major failure of a Badger channel, so I took the amps out of my system until I figure out why it blew up. I may post a picture of that pcb in the Badger build thread for some help.
I just started stuffing the TGM8 boards, so it will be a while before they can be compared to the Badger. Also, I had a major failure of a Badger channel, so I took the amps out of my system until I figure out why it blew up. I may post a picture of that pcb in the Badger build thread for some help.
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I use these vinyl "condoms" which snugly fit over PCB mounted fuseclips and provide electrical insulation, so a dropped screwdriver or wayward bare wire can't touch the exposed metal at either end of the fuse.
Fuse Covers: Cylindrical Fuse, 2AG, 3AG, 5mm Fuses: Keystone Electronics
They are fairly cheap, Mouser's part number for the 5x20 is 534-3527C
An ounce of prevention is worth 49 cents in my opinion.
Fuse Covers: Cylindrical Fuse, 2AG, 3AG, 5mm Fuses: Keystone Electronics
They are fairly cheap, Mouser's part number for the 5x20 is 534-3527C
An ounce of prevention is worth 49 cents in my opinion.
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Looks nicely constructed. I notice the socket for the LED, presumably so you can mount the LED on the front panel - nice touch.
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Yeah, that strike is starting to irritate many... I've started to use other services, like FedEx, UPS, Purolator, etc... The people at Canada Post barely open the door at the office and throw boxes on the floor, not even waiting for us to pick them up... I had a girl from UPS delivering boxes at the same time and she couldn't believe it.
It might be quicker / cheaper to re-order from China and select a different shipper.
Don't know about Canada but in USA when I order boards from the cheapest fab (Elecrow) and select 5 day DHL shipping (costs USD 22), DHL carries the package every single mile of the trip, including The Last Mile. A DHL van pulls up to my house, out pops a DHL employee wearing a DHL uniform, who rings my doorbell, gathers my signature, and hands over the parcel which is encased in a bright yellow DHL shipping envelope. US Postal Service NEVER TOUCHED my PCBs.
Don't know about Canada but in USA when I order boards from the cheapest fab (Elecrow) and select 5 day DHL shipping (costs USD 22), DHL carries the package every single mile of the trip, including The Last Mile. A DHL van pulls up to my house, out pops a DHL employee wearing a DHL uniform, who rings my doorbell, gathers my signature, and hands over the parcel which is encased in a bright yellow DHL shipping envelope. US Postal Service NEVER TOUCHED my PCBs.
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They still didn't arrive. I think the issue is with Canada Post not the supplier. However, I sent them a message today to suggest what you said - run a batch at their cost and I'll pay extra for 'proper shipping' I was hoping to avoid being out of pocket but the frustration I feel is worth some extra cost to avoid !
I ordered 10 boards, which is 5 pairs and currently on the list is:
1/ 'thimios' (paid up front)
2/ 'ian finch' (paid up front)
3/ 'minek123' (recently enquired)
4/ available
5/ available
I ordered 10 boards, which is 5 pairs and currently on the list is:
1/ 'thimios' (paid up front)
2/ 'ian finch' (paid up front)
3/ 'minek123' (recently enquired)
4/ available
5/ available
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Canada post.... I lost two packages.
One from Do and another from Jeff.
Unfortunately, it is a familiar problem nowadays...
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As my one Canadian girlfriend said, repeatedly: Soar-ee.
Soar-ee that my successful and TOTALLY WINNING FOR SURE strategy, did not work for you. At least I made an effort. It was a complete failure at your house, despite the prior experience of working quite well at my house, but at least I made an effort. Upon realizing this, I have a premonition: there might be individuals here who made no effort at all, OBVIOUSLY no effort, you can review prior posts before deciding.
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