For those who are having trouble sourcing the .22 5W resistors. Here's a link;
0.22 Ohm 5W Resistor Wire Wound 5% Tolerance
Ron
0.22 Ohm 5W Resistor Wire Wound 5% Tolerance
Ron
There are three transistor pairs for one channel. The (TP1-TP2)/0.44 ohms only represent current flow through one out of three pairs.Okay, I have everything replaced. I replaced everything on the heatsink for that channel. So outputs, drivers, and the VBE transistor. I meticulously triple checked for shorts between heatsink and all tabs/pins on each of those devices. All looks good.
Cross my fingers and fire it back up. So far so good. Let the amp run for 10-15 min with no issue. Trim off the offset. No issue. Start to trim up R30 again (VERY carefully this time, making sure to go slowly so as not to over-turn it again). So far so good. Get it dialed in right where I want it (to match the other working channel) at 25-26mv across TP1/TP2. I'm within 1-2mv of that, trying to dial in the last bit. Then the 4A on-board fuses die again! No, my hand didn't slip and accidentally short something either.
However, this time, there is no short on my output devices (or any other short to the heatsink). They show dozens of M Ohms. In fact, I can still power it up and the other channel will work fine (no mains fuse failure). It's setup the exact same way... no offset, 26mv across TP1/TP2.
Is it possible that some transient occurred while I'm turning the trimmer, causing some quick current draw?
I'm considering putting the temporary 10ohm resistors back instead of the fuses to compensate, but I wanted to check if that's a good idea before I burn another set of output devices. What do you think?
I haven't touched R7 yet (and I forgot to check it before installing it). Could that be contributing (the CCS adjustment)? It's 200 ohm trimmer, but I have no idea what it's set at right now.
Thanks again!
The instruction assume all three transistor pairs are very close to each other.
If your transistors do not match well, other transistor pair may consume much more current than the pair monitored by the TP1/TP2.
If you don't have oscillation, after setting TP1/TP2, also check the voltage drop for other two pairs.
Any given pair exhibit very voltage drop may be the reason why fuse blow even though heat sink is not very hot. Heat conductivity take times.
After identifying the transistor pair with highest voltage drop, while try to set TP1/TP2 to your desire value, monitor the temperature (as well as voltage) of this transistor pair, it could be very hot within few seconds before fuse blown.
Rather a long thread here, 121 pages so far.
Is there a BOM with components chosen for higher voltage rails? >/= +/- ~63V ?
I've got a wonderful old Hafler that has offered it's TX as a donor transplant.
Trying to figure figure out part(s). ie; BC546-AP 65V max, a little close for comfort.
I wouldn't do this to capacitors.
Thanks,
Ron
Is there a BOM with components chosen for higher voltage rails? >/= +/- ~63V ?
I've got a wonderful old Hafler that has offered it's TX as a donor transplant.
Trying to figure figure out part(s). ie; BC546-AP 65V max, a little close for comfort.
I wouldn't do this to capacitors.
Thanks,
Ron
I thought I had read someone had used this one too. Thanks for answering!
Could I pick your brain a little bit?
Because the voltages +/-63 (rails) are a little higher, did you have to use different parts than on the BOM? (JoJoD818 Ver. 2 on 1/16/2013)
http://www.diyaudio.com/forums/imag...n/P-DIYAB-2V20/P-DIYAB-2V20-diyAB-amp-bom.xls
Do you have YOUR BOM still?
Can do PM's if more appropriate.
I'm almost competent enough to build this amp. (With lots of help)
Not so easy a cave-man can do it.
Thanks,
Ron
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I thought I had read someone had used this one too. Thanks for answering!
Could I pick your brain a little bit?
Because the voltages +/-63 (rails) are a little higher, did you have to use different parts than on the BOM? (JoJoD818 Ver. 2 on 1/16/2013)
http://www.diyaudio.com/forums/imag...n/P-DIYAB-2V20/P-DIYAB-2V20-diyAB-amp-bom.xls
Do you have YOUR BOM still?
Can do PM's if more appropriate.
I'm almost competent enough to build this amp. (With lots of help)
Not so easy a cave-man can do it.
Thanks,
Ron
I'm sorry, I don't remember exactly which parts I used. Have you downloaded the build documents? It is a lot to read but they took the time to explain a lot of the choices. Many of my choices were based on devices I had on hand. I had a lot of Onsemi parts so where I could I used those. The build documents give you a lot of choices.
Thanks OS and 4Given,
There seems to be a few different threads about building "The Badger". Any chance for a link to the build documents?
My head is swimming after reading most of the pages of this thread. Starting to understand what some parts do. Maybe not.
Thanks for the future help.
I think the extra oomph will help the sound from my Thor's. A few more watts than the F5. (Which I really like!)
Ron
There seems to be a few different threads about building "The Badger". Any chance for a link to the build documents?
My head is swimming after reading most of the pages of this thread. Starting to understand what some parts do. Maybe not.
Thanks for the future help.
I think the extra oomph will help the sound from my Thor's. A few more watts than the F5. (Which I really like!)
Ron
That's the one. I recommend reading all the way through it before you start the build. This is a good amp to learn from.
My Badger is running +/-63V without any problems. As Os said some caps must be 100V.
My next pair will have split LTP and VAS sources like in Volverine so tracks must be cut in a couple of places. Boards are already marked for cutting. I need to find time to do the rest.
Choice of transistors and some quality components may also make small difference plus a few minor resistor/cap value changes.
cheers,
My next pair will have split LTP and VAS sources like in Volverine so tracks must be cut in a couple of places. Boards are already marked for cutting. I need to find time to do the rest.
Choice of transistors and some quality components may also make small difference plus a few minor resistor/cap value changes.
cheers,
I thought the Honey Badger has the option to add cascodes to the input LTPs.
The risk of overvoltage of the input devices is removed if you adopt that option.
Thanks all,
I will read through the build guide many times before I warm up the soldering Iron.
I ordered the boards and a bucket of various 1% metal film R from "The Bay", which will be tested and verified before populating. I'll start to sort through my pile of caps and find what works and order the Q's from Digikey later.
Andrew T, Your post was useful. I'll look into that option.
Ron
I will read through the build guide many times before I warm up the soldering Iron.
I ordered the boards and a bucket of various 1% metal film R from "The Bay", which will be tested and verified before populating. I'll start to sort through my pile of caps and find what works and order the Q's from Digikey later.
Andrew T, Your post was useful.
I'll look into that option.Ron
i confirm, i just followed the instructions and presets mentioned and the amp worked the first time...
Hi folks,
I'm back again after a few more sets of blown outputs.
Let me address some of the questions/suggestions already posted and then I'll add some more info.
What I did notice, however, is that the voltage would drift around quite a bit. It would drift from 10mv to 15mv over the course of a min or two. I'd goose the bias down to ensure it never got above 15mv or so. It'd drift back down. Then back up. And so on and so forth (all the while, I'd stop to check temps). After about 15min of this, BAM. Blown.
I'm a little at a loss here. I'm considering popping out the bias trimmer from the working channel, measuring it, and using a fixed resistor for the broken one.
Anyway, thanks again for all your help.
I'm back again after a few more sets of blown outputs
.Let me address some of the questions/suggestions already posted and then I'll add some more info.
Agreed! My outputs are wired up through a speaker protect board to terminal posts on the chassis. No flying leads or anything so I really don't see how that would have happened.Thanks for the idea, though! Oh, and yes I used 0.22ohm emitter resistors.
AH okay, that makes sense. This time I strapped my 100MHz analog scope to the output of the amp as I increased the bias. I didn't notice any activity on the output at all to indicate oscillation. I also never noticed any significant heat being dissipated from any of the devices.
So I'm on about my 4th set of output devices, all from the same lot. While I didn't hand-match them, would you still expect such a large mismatch as to cause issues? I'd be surprised, but stranger things have happened. I'll try to monitor all 3 sets this time.
Okay, so this time around, I replaced all the transistors on the board. Replaced the trimmers. I double checked all resistor values (both by codes and by measuring), checked all joints for shorts. Cleaned up the PCB to ensure no tiny debris causing shorts. Started from scratch. Was able to trim off the offset again, no problem. SLOWLY turned up the bias, 1/4 a turn at a time. When I started to get to ~10mv I let the amp sit for a few min. In the meantime, I continuously checked the temp of everything with my cheapo radio shack IR thermometer. Nothing ever got above ~105F. Output devices were well below 90F. The VAS and CCS devices got the hottest at ~105F, but not alarmingly so. They are fitted with large heatsink. A few resistors got a little hot, but again, nothing out of the ordinary.
What I did notice, however, is that the voltage would drift around quite a bit. It would drift from 10mv to 15mv over the course of a min or two. I'd goose the bias down to ensure it never got above 15mv or so. It'd drift back down. Then back up. And so on and so forth (all the while, I'd stop to check temps). After about 15min of this, BAM. Blown.
I'm a little at a loss here. I'm considering popping out the bias trimmer from the working channel, measuring it, and using a fixed resistor for the broken one.
Anyway, thanks again for all your help.
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