Paranoid ? - "criticism" would be me saying,"he is an idiot - don't listen to him".
EDIT - conversely ... when a output stage is saved or the "dead silence" of the badger/slewmaster
designs are discussed , I attribute this to " Andy T" recommendations.
I did not do that , I asked for a simple "what and why"
for your recommendation (X7R).
Just the "X7R" would of been sufficient for any halfwit to Google (me included-.
now I know.) .
I would of known previously , just with a quick concise answer.
In fact .... I agree , there are more ideal HF decoupling options.
Nothing was specified for the .1u's , so your recommendation
would be worthy to update the BOM. Many who have built it
most likely used whatever poly/ceramic was in the "junkbox".
OS
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This is actually a subject I've been trying to learn more about for a while. Searching the forums and reading leads to a lot of contradiction and confusion. There seems to be a lot of different opinions on any talk about capacitors.
I just wanted to know whether "don't" meant a grave safety concern , or a
better performing decoupling arrangement.
I have not seen any poly's actually blow up , long term .
Even on a poly Zoble , the resistor will smoke before the cap will fail
. OS
Because there are many of us who a merely hobbyists and neophytes, who, like me, don't know the right questions to ask.
This is why we look to knowledgeable people such as yourself for answers.
I've repeated myself many time teaching someone (who wanted to learn) how to cut a hip/valley rafter intersection.
We appreciate you knowledge Andrew, thank you for sharing. (not sarcastic)
Ron
Starting Problem
So... I began building my Honey Badger 3 months ago (I've been taking my time.) It's a dual mono configuration: Two 40/40 625VA transformers, 2 PSU boards each with 40,000uF per rail. I also installed the soft start and speaker protection boards.
I assembled everything in my chassis today, and starting connecting one component at a time to power.
Everything up the chain worked great and measured as expected (soft start board, each transformer, the PSUs, the smaller transformer for the speaker protection board, the speaker protection board) until I got to powering on the actual honey badgers.
I made sure all the trimmers were set as required in the build guide. I double checked to make sure there were no shorts between any of the outputs and the heatsink. Nothing was connected at the inputs or outputs. I replaced the fuses with the 10 ohm 1 watt sacrificial resistors. I placed the spring clips of my multimeter across one of the resistors, and I flicked it on.
Both lights turned on, but the voltage skyrocketed well beyond the .5V maximum. It got above the 2V setting of my multimeter before I could flick it back off. Nothing burst into flames, no burning smell, no clicks or flickers. Same exact result with the second board.
Where do I begin to troubleshoot this?
So... I began building my Honey Badger 3 months ago (I've been taking my time.) It's a dual mono configuration: Two 40/40 625VA transformers, 2 PSU boards each with 40,000uF per rail. I also installed the soft start and speaker protection boards.
I assembled everything in my chassis today, and starting connecting one component at a time to power.
Everything up the chain worked great and measured as expected (soft start board, each transformer, the PSUs, the smaller transformer for the speaker protection board, the speaker protection board) until I got to powering on the actual honey badgers.
I made sure all the trimmers were set as required in the build guide. I double checked to make sure there were no shorts between any of the outputs and the heatsink. Nothing was connected at the inputs or outputs. I replaced the fuses with the 10 ohm 1 watt sacrificial resistors. I placed the spring clips of my multimeter across one of the resistors, and I flicked it on.
Both lights turned on, but the voltage skyrocketed well beyond the .5V maximum. It got above the 2V setting of my multimeter before I could flick it back off. Nothing burst into flames, no burning smell, no clicks or flickers. Same exact result with the second board.
Where do I begin to troubleshoot this?
What voltage , what bulbs ?
A 10R resistor as fuse would go above 2V with only 60 or so ma per output
(180ma outputs + 23 ma for the drivers/VAS/IPS).
Increase the bias trimmer to max value - 500R. Then you should only have
the driver/VAS/input stage current (.2-.3V only) across that 10R.
I just did 4 similar OPS's ... drivers only first.
Another test point is across the main driver Re (R36 = 150R).
It will read < 1.1V before the outputs start to conduct.
OS
Sorry, bulbs? (I'm new at this)
I will double check once I get home, but I am 99.99999% certain that the bias trimmers are set at 500r. Assuming they are, what should I look at next?
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With this situation , I would check every diode and semi B-E junction .
Confirm you have the correct gender semi's and double check for resistor
"mistakes" on the 1/4 watter's . A 8.2R for the R27 would overbias things nicely.
PS- R27 and R14 (the CCS's) are also good things to make current checks on.
They are the "heart" of this amp - operation wise.
OS
Thanks! I'll check everything out and let you know. I'm thinking, since it's the same problem with both boards, that I mis-ordered a part.
I'm just starting my HB build. Since I don't possess the level of audio amp building knowledge that many do around here, I rely solely on the BOM and trust that the designer has offered more advice about the proper component (type, rating, etc.) he has chosen to include in the parts list. More is always better in this regard. In fact, I bet many DIY'ers do. If it's not critical then say so, if it is, say so too and be precise about the type of part. I'm not saying yours are, but a BOM should be very precise with what it recommends and what type, quality, etc. to use. Most people can't play a guessing game when it comes to electronics parts required to fulfill the designers intentions. Looking through Mouser can be intimidating at best, and make you hopelessly lost at worst.
Rick
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I read and tested every resistor. They're all correct. I checked the part number and orientation of all the semi's. They're fine. I looked at every solder joint to make sure there was nothing wrong. All good.
Guess it's time to remove the diodes and check them...
Most diodes can be checked in-circuit.
You said nothing smoked or popped , do that quick power-on test while
reading across R32 or R33. Each should read (or jump to) - no more than .3V (>15ma).
Then you will know whether it is a LTP/CCS/VAS issue or a output stage issue.
And , with the same quick power on test , read those 2 CCS currents.
OS
Re -check you semi's.
If you are not using the incandescent lamp method of limiting current (and a fuse) ,your 10R's
need to be 3-5W for the OPS current draw.
I use the "small amp method" - just build the amp to the driver stage (mje15032/33),
2 -1k resistors to the output trace/feedback ..... set to 1.1V (R36) - outputs will not draw current when installed.
PS - I can use small 10R's , as I am only testing everything BUT the outputs.
The .35V across R32 is a good sign , your low current section seems fine.
Since you were able to even get a reading before r34 blew - no "Hard short".
This leaves the Vbe/drivers/outputs.
Edit - what value do you use for R27 ? 56/68R increases OPS bias (82 is perfect) ... also, R28-R30
are crucial to achieve proper bias.
OS
If you are not using the incandescent lamp method of limiting current (and a fuse) ,your 10R's
need to be 3-5W for the OPS current draw.
I use the "small amp method" - just build the amp to the driver stage (mje15032/33),
2 -1k resistors to the output trace/feedback ..... set to 1.1V (R36) - outputs will not draw current when installed.
PS - I can use small 10R's , as I am only testing everything BUT the outputs.
The .35V across R32 is a good sign , your low current section seems fine.
Since you were able to even get a reading before r34 blew - no "Hard short".
This leaves the Vbe/drivers/outputs.
Edit - what value do you use for R27 ? 56/68R increases OPS bias (82 is perfect) ... also, R28-R30
are crucial to achieve proper bias.
OS
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Yes, I did my own hip and valley with a Dormer inserted into the hip, when I built my house.
I use and recommend you always power up via a Mains Bulb Tester.
If there is excessive power demand the bulb lights up and reduces the input to the mains transformer to a few volts. This results in only one or two volts from the secondary and the amplifier (or whatever) is saved from damage.
I also recommend that "saver" diodes (1n4002) are added to the amplifier PCB.
One from each supply rail to the output line
and
one from each supply rail to power ground.
These prevent reverse voltages being applied and again saves the components from damage.
Using resistor in lieu of fuses does not protect amplifier components. Fuses are too slow to save a semiconductor. Resistors are even slower.
There is ONE situation where these resistors are useful:
AFTER proving that the amplifier is working properly, you can monitor the current from the supply rails via the voltage drop on these resistors. Some amplifiers do not have other resistors that can be used to monitor operating currents and in these assemblies an extra pair of fuse holder resistors can help with checking operating currents.
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Howdy, I will probably chicken out, but instead of 220 uf np cap, I used two 470 uf polar in opposite orientation to each other. The thing I have done that I was not suggested by anyone to do was put a schottky diode in series with each, cathode to positive pole on each. Will this work? Is it a bad idea? Any thought? Thanks.