100v vs. 101v, I would just connect a few caps to the power
supply and hook everything up to see what the loaded voltage is
before trying to solve the problem. It should sag some and maybe
you are good.
Other ideas, add some series diodes to reduce the voltage or
unwind the secondary a bit. /hehe
supply and hook everything up to see what the loaded voltage is
before trying to solve the problem. It should sag some and maybe
you are good.
Other ideas, add some series diodes to reduce the voltage or
unwind the secondary a bit. /hehe
Well, I got the inrush thermistors and the 0R22 6W resistors today. All I need to do is wait for the MJE340, the 2SC and 2SA devices and the heat sink and I'm ready to finish assembly. I soldered in the resistors today, and that about completes assembly for the passive components. I'm very very eager to get everything and try it out. I'm also using silpad for the heatsinks. Just thought I'd let you guys know.
emuman100 hows the build coming?
I am just about to embark on an AV800 build.
I just finished designing an inrush scheme and a output delay/dc speaker protection.
I will be powering up the AV800 boards later next week, without the output devices, for testing and setup, if all goes well I should have a working stereo AV800 within a month or so.
The biggest and most expensive hurdle I find is building a case to house it all in, I have not yet had a chance to set up my shop properly since the move and I find aluminum is very expensive from the only supplier I have found where I now live.
Do you have any pictures of what you have accomplished so far? I would be interested in seeing anything you have, especially your heat sink.
Thanks!
I am just about to embark on an AV800 build.
I just finished designing an inrush scheme and a output delay/dc speaker protection.
I will be powering up the AV800 boards later next week, without the output devices, for testing and setup, if all goes well I should have a working stereo AV800 within a month or so.
The biggest and most expensive hurdle I find is building a case to house it all in, I have not yet had a chance to set up my shop properly since the move and I find aluminum is very expensive from the only supplier I have found where I now live.
Do you have any pictures of what you have accomplished so far? I would be interested in seeing anything you have, especially your heat sink.
Thanks!
Banned
Joined 2002
This is my case for my AV800 Stereo Amp.
http://www.briangt.com/gallery/album01/DSC00149
Regards
Anthony
http://www.briangt.com/gallery/album01/DSC00149
Regards
Anthony
Help!!!
Look at the picture.
For those of you who have tested this board, is ground connected at unmarked hole #1 or unmarked hole #2?
#1 appears to be ground to me and #2 is the same as signal ground.
Also the pre-flight test states that a 10 ohm 1/4 watt resistor is to be soldered between one side of R38 and the output but it doesn't say which side of R38 so I connected the resistor between the two points shown with the blue arrows.
Anthony Holton has again dissappeared and is not responding to his email or I would already have answers to these questions.
I want to finish the preflight testing today and get my output devices mounted and get both modules bolted down to the heatsink so I can fire the whole mess up and have a listen, so your help here would be greatly appreciated.
Thanks all!
An externally hosted image should be here but it was not working when we last tested it.
Look at the picture.
For those of you who have tested this board, is ground connected at unmarked hole #1 or unmarked hole #2?
#1 appears to be ground to me and #2 is the same as signal ground.
Also the pre-flight test states that a 10 ohm 1/4 watt resistor is to be soldered between one side of R38 and the output but it doesn't say which side of R38 so I connected the resistor between the two points shown with the blue arrows.
Anthony Holton has again dissappeared and is not responding to his email or I would already have answers to these questions.
I want to finish the preflight testing today and get my output devices mounted and get both modules bolted down to the heatsink so I can fire the whole mess up and have a listen, so your help here would be greatly appreciated.
Thanks all!
Hmmmmmmm
OK so I got the 47K resistor in place and fired it up again.
I have come to the conclusion that my new Variac is worth it's weight in gold...
So I fire up the AV800 and as I am raising the voltage (90-92V is the target) I get to about 50Vdc and R1, R2, R3 and R4 start to get really hot, I mean REALLY hot, so I shut everything down and check the values of these resistors against the construction guide and measure the value of each resistor, the color code corresponds to the values in the construction guide and the measured values check out too, whew didn't ruin these resistors.
Now my question is, in the UPDATED construction guide in the preflight section it no longer says that Q8 should be soldered in for the test, was that an omission or is it an error to solder in Q8 for the preflight test?
I am getting so damned frustrated, I don't have a proper schematic as the one in the original construction guide was the wrong schematic, Anthony promised me a replacement (YA RIGHT), The silk screen has mistakes and the parts list I now find has errors as well, how is anyone to build this amplifier without proper documentation?
Has anyone ever known anyone, besides Anthony, to get one of these amplifiers working, I have searched the web but there doesn't seem to be many references to Anthony's AV800's except here, on Anthony's page and I found THIS one, of course even on Anthony's page he has removed all reference to the AV800 except for PCB sales and the construction guide.
So here I go trying to reverse engineer this board to try and find mistakes, guess I'll have to first draw a schematic based on how the board is designed,Then I will have to look for any obvious errors, and finally I'll have to do some math and simulations to see if it should work.
I am fairly new to this amp building game and this stuff doesn't come second nature to me yet so it takes me a while to look at things and try to figure out whats wrong. Arrrrggggghhhhhh!
I am open to ideas here... ANYONE????
Updates as they come.
OK so I got the 47K resistor in place and fired it up again.
I have come to the conclusion that my new Variac is worth it's weight in gold...
So I fire up the AV800 and as I am raising the voltage (90-92V is the target) I get to about 50Vdc and R1, R2, R3 and R4 start to get really hot, I mean REALLY hot, so I shut everything down and check the values of these resistors against the construction guide and measure the value of each resistor, the color code corresponds to the values in the construction guide and the measured values check out too, whew didn't ruin these resistors.
Now my question is, in the UPDATED construction guide in the preflight section it no longer says that Q8 should be soldered in for the test, was that an omission or is it an error to solder in Q8 for the preflight test?
I am getting so damned frustrated, I don't have a proper schematic as the one in the original construction guide was the wrong schematic, Anthony promised me a replacement (YA RIGHT), The silk screen has mistakes and the parts list I now find has errors as well, how is anyone to build this amplifier without proper documentation?
Has anyone ever known anyone, besides Anthony, to get one of these amplifiers working, I have searched the web but there doesn't seem to be many references to Anthony's AV800's except here, on Anthony's page and I found THIS one, of course even on Anthony's page he has removed all reference to the AV800 except for PCB sales and the construction guide.
So here I go trying to reverse engineer this board to try and find mistakes, guess I'll have to first draw a schematic based on how the board is designed,Then I will have to look for any obvious errors, and finally I'll have to do some math and simulations to see if it should work.
I am fairly new to this amp building game and this stuff doesn't come second nature to me yet so it takes me a while to look at things and try to figure out whats wrong. Arrrrggggghhhhhh!
I am open to ideas here... ANYONE????
Updates as they come.
UPDATE-- PROBLEMS FOUND
First off this is the resistor I burned up this morning:
Second look at this:
This is Q1, Q2, Q6 and Q7...
Look at the silkscreen outline of Q1 (2SC2240), it shows C B E but after digging up a datasheet on the web here is what I found
Correct me if I am wrong but doesn't this show E C B ?
Of course if you look at the updated construction manual the schematic shows a 2SC254 for Q1 and Q2 but the parts list still shows 2SC2240?!?!?!
My datasheet for the BC546 (Q6 and Q7) shows the C B E silkscreen to be correct.
So I guess this is my fault for not checking the datasheet before inserting Q1 and Q2. Checking around the web today I wasn't able to find a datasheet for a 2SC2240 that had any other pinout, I even checked NTE for a cross and it shows E C B as well.
The new construction guide lists Q23 as an IRF610 but the symbol on the new schematic shows a standard NPN transistor.
The new guide also lists the following changes R54 from 10K (old guide) to 100ohms and R56 from 100ohms (old guide) to 10K
switching these two resistors makes sense.
Holy crap, no wonder I don't see any links on the web to completed AV800 amps, there are probably a lot of people sitting around with AV800 boards in their junk bins cause they got tired of replacing burned up parts.
The question now is have I found all the errors yet or have I just scratched the surface, one does have to wonder
As always, updates as they happen.
FRAZZLED
First off this is the resistor I burned up this morning:
An externally hosted image should be here but it was not working when we last tested it.
Second look at this:
An externally hosted image should be here but it was not working when we last tested it.
This is Q1, Q2, Q6 and Q7...
Look at the silkscreen outline of Q1 (2SC2240), it shows C B E but after digging up a datasheet on the web here is what I found
An externally hosted image should be here but it was not working when we last tested it.
Correct me if I am wrong but doesn't this show E C B ?
Of course if you look at the updated construction manual the schematic shows a 2SC254 for Q1 and Q2 but the parts list still shows 2SC2240?!?!?!
My datasheet for the BC546 (Q6 and Q7) shows the C B E silkscreen to be correct.
So I guess this is my fault for not checking the datasheet before inserting Q1 and Q2. Checking around the web today I wasn't able to find a datasheet for a 2SC2240 that had any other pinout, I even checked NTE for a cross and it shows E C B as well.
The new construction guide lists Q23 as an IRF610 but the symbol on the new schematic shows a standard NPN transistor.
The new guide also lists the following changes R54 from 10K (old guide) to 100ohms and R56 from 100ohms (old guide) to 10K
switching these two resistors makes sense.Holy crap, no wonder I don't see any links on the web to completed AV800 amps, there are probably a lot of people sitting around with AV800 boards in their junk bins cause they got tired of replacing burned up parts.
The question now is have I found all the errors yet or have I just scratched the surface, one does have to wonder
As always, updates as they happen.
FRAZZLED
Kilentra said:
Yes... If you look on page 6 of the new construction guide it outlines one of the more well known silkscreen errors, personally I think this should be printed on PAGE 1 because on page 4 Anthony has you doing pre-flight testing when in fact a DIY'er might not have read as far as page 6
Perhaps I am asking too much but it would be nice to have a parts list, schematic and PCB that match, this hunting around for errors is getting expensive in both time and ruined parts, or if Anthony would be kind enough to answer his email or update his site with new information about PCB errors
Dang, alright... stick with it, common sense will fix your amplifier. Make sure the PCB traces match the schematic in the areas of concern. Ignore the parts list for now.
The sym amp uses the same layout for the cascoded input stage with all BC546's (lower voltage). Try flipping the 2240s around, or use any other NPN transistor with a Vceo of 100V+. The reversal of Q1 and Q2 would normally cause the stage not to conduct but you might have a problem in the current sources... check the overall currents by measuring voltages on R54 and R3.
The difference in using a Mosfet instead of a transistor for Q23 is the input stage current would be reduced to 1.1 mA instead of 1.4 mA. I wish I knew how that impacted the amp's performance. I would use the NPN transistor because that is what works correctly in the sym amp, the schematic says BD681 but you could probably use a MJE340 or BD139, too.
The schematic I have shows two resistors named R54. The one in the input stage should be 10k and the one in the VAS current mirror should be 100 ohms.
It's not really expensive and time consuming until you start blowing output stages.
The sym amp uses the same layout for the cascoded input stage with all BC546's (lower voltage). Try flipping the 2240s around, or use any other NPN transistor with a Vceo of 100V+. The reversal of Q1 and Q2 would normally cause the stage not to conduct but you might have a problem in the current sources... check the overall currents by measuring voltages on R54 and R3.
The difference in using a Mosfet instead of a transistor for Q23 is the input stage current would be reduced to 1.1 mA instead of 1.4 mA. I wish I knew how that impacted the amp's performance. I would use the NPN transistor because that is what works correctly in the sym amp, the schematic says BD681 but you could probably use a MJE340 or BD139, too.
The schematic I have shows two resistors named R54. The one in the input stage should be 10k and the one in the VAS current mirror should be 100 ohms.
It's not really expensive and time consuming until you start blowing output stages.
I have 3 different revisions of the AV800 document.
Each document has some typographical errors to some degree,
but the latest document seems worse than the previous document.
I don't have the original AV800 document right now to compare
but it appears that the new document resembles the original
more, which had 'less circuits' .....
I have document build 22022001 (older) and 03022004 (newest).
The new document doesn't have these components on the
schematic.
On the buffer stage, there are two zener diodes, one diode
across each mosfet (Q5/Q6) on gate and source terminals,
like so;
ZD3 - 1N4737 (used on Q5).
ZD4 - 1N4737 (used on Q26).
Also, removed was ZD5, ZD6 (6.8v zeners), and D3, D4 diodes.
I think this network is to clamp the signal if overdriven and I don't
think the omission of these parts is mission critical, it should
work. I have a faint memory that the original AV800 didn't
have these parts, then these parts were added, now not
show again. :huh ? :
There is some schematic part number errors on the new document.
The old document shows;
Q23 = BD681
Q1 = 2SC2240
Q2 = 2SC2240
Q3 = 2SA1306
Q4 = 2SA1306
Q24 = 2SC3298
Q25 = 2SC3298
I see some reference designators that changed but the
component values are the same on these two schematics.
New designator, old designator
R42 is now called R32
R54 is now called R56
The old document has one error that I can see, there are
two resistors that use the R54 reference designators.
R54 on BD681 is 10k ohms
R54 on 2SC3298 is 100 ohms
The new document fixed the resistor on BD681 and called it
R56, 10k ohms.
It appears that document --> 22022001 of the AV800 has
much less errors than the new one because I spent about 3
months staring at it when I did my board layout.
For now, I would go with what I posted and forget the parts
list, just rely on the schematic AND double check the silkscreen
on your boards by following the traces to make sure you
are installing the parts correctly.
Does your pcb board have ZD3, ZD4, ZD5, ZD6, D3, D4 ?
If not, it should work but you might want to install those later.
I have some original AV800 pcbs and I think they don't have
those parts either.
Each document has some typographical errors to some degree,
but the latest document seems worse than the previous document.
I don't have the original AV800 document right now to compare
but it appears that the new document resembles the original
more, which had 'less circuits' .....
I have document build 22022001 (older) and 03022004 (newest).
The new document doesn't have these components on the
schematic.
On the buffer stage, there are two zener diodes, one diode
across each mosfet (Q5/Q6) on gate and source terminals,
like so;
ZD3 - 1N4737 (used on Q5).
ZD4 - 1N4737 (used on Q26).
Also, removed was ZD5, ZD6 (6.8v zeners), and D3, D4 diodes.
I think this network is to clamp the signal if overdriven and I don't
think the omission of these parts is mission critical, it should
work. I have a faint memory that the original AV800 didn't
have these parts, then these parts were added, now not
show again. :huh ? :
There is some schematic part number errors on the new document.
The old document shows;
Q23 = BD681
Q1 = 2SC2240
Q2 = 2SC2240
Q3 = 2SA1306
Q4 = 2SA1306
Q24 = 2SC3298
Q25 = 2SC3298
I see some reference designators that changed but the
component values are the same on these two schematics.
New designator, old designator
R42 is now called R32
R54 is now called R56
The old document has one error that I can see, there are
two resistors that use the R54 reference designators.
R54 on BD681 is 10k ohms
R54 on 2SC3298 is 100 ohms
The new document fixed the resistor on BD681 and called it
R56, 10k ohms.
It appears that document --> 22022001 of the AV800 has
much less errors than the new one because I spent about 3
months staring at it when I did my board layout.
For now, I would go with what I posted and forget the parts
list, just rely on the schematic AND double check the silkscreen
on your boards by following the traces to make sure you
are installing the parts correctly.
Does your pcb board have ZD3, ZD4, ZD5, ZD6, D3, D4 ?
If not, it should work but you might want to install those later.
I have some original AV800 pcbs and I think they don't have
those parts either.
Kilentra said:
This is exactly my approach now.
I removed the 2240's (Q1 & Q2) and tested them against the only new one I have on my Sencore TF46 Super Cricket and they tested as new. I wish I could measure R54 and R3 but I would have to have the board submersed in a vat of liquid nitrogen just to keep things cool enough, I haven't been able to get the power supply up over 20Vdc yet without causing some heat (100+ F) in some resistors.
I am sticking with the BD681 for now, as I have quite a few spares.
Yes... This is what I found in the original schematic as well. I installed new resistors of proper values and fired the amp up again but now R54 and R56 are heating up as well as R2 and R4 or was it R1 and R3, damn forgot to write it down.
It's not really expensive and time consuming until you start blowing output stages.
This is true but I only have so many replacement parts kicking around, soon I'll have to start driving down to the parts shop or ordering stuff online. I am afraid that by the time I get all the errors straightened out and fix my second PCB, one board will look pristing and new while the other will look like FRANKENSTEIN with all the burn marks all over it.
For reference only;
Looking at the AV400 document, ZD3 and ZD4 zeners.
On the old AV800 document, there are two zeners installed in
the same fashion, they are 6.8v zeners. But, he also has
another series diode installed per zener, where the anodes
are connected together. I'm taking a guess and saying they
are 1N400x family as the parts list nor schematic shows value.
I'm guess that is clamping that input voltage to the
output stage ~ 7.5v (6.8V zener + 0.7v diode) ?
Looking at the AV400 document, ZD3 and ZD4 zeners.
On the old AV800 document, there are two zeners installed in
the same fashion, they are 6.8v zeners. But, he also has
another series diode installed per zener, where the anodes
are connected together. I'm taking a guess and saying they
are 1N400x family as the parts list nor schematic shows value.
I'm guess that is clamping that input voltage to the
output stage ~ 7.5v (6.8V zener + 0.7v diode) ?
thylantyr said:I have 3 different revisions of the AV800 document.
Each document has some typographical errors to some degree,
but the latest document seems worse than the previous document.
I don't have the original AV800 document right now to compare
but it appears that the new document resembles the original
more, which had 'less circuits' .....
I have the 3 documents as well, what a mess, things are supposed to get better with each revision.
<SNIP>
Nope don't have those parts on my PCB. I will just follow the schematic for now but this is going to take some time.
Updates as they happen.
Yes, check the transistors, maybe one of them somehow got damaged. One of the problems I had in my sym amp was somehow the Zener diode in the cascoding was damaged, lowering the breakdown voltage. I turned the amp on and I was prodding around when one of the BC546's exploded. (By the way, one of my PCBs is pretty ripped up, with a lot of wires bypassing broken traces or pads. But it works wonderfully.)
The Zener and diode in series are there to limit gate voltages, I think. I am not sure why you need a diode in addition to the Zener. Any diode works.
You said it was R1-4 and the R54's which get hot. Please, try to measure the voltage on as many of these resistors as you can.
The Zener and diode in series are there to limit gate voltages, I think. I am not sure why you need a diode in addition to the Zener. Any diode works.
You said it was R1-4 and the R54's which get hot. Please, try to measure the voltage on as many of these resistors as you can.
OK...
I just spent the past hour comparing the schematic to the pcb and parts installed. I can't seem to find any further errors but then again my eyes are about to fall out of my head from all the staring
I am beginning to suspect my Zeners are either defective from the problems or perhaps were defective right from the wholesaler.
R3, R4, R54 and R57 get pretty hot (100+ F) when the power supply voltage gets to 20Vdc. I can't turn up my variac beyond that or they will start to smoke.
I have tested most of the transistors and they all test as new (comparing to my as yet untested AV800 board) so as a precaution I am going to pick up some new Zeners and install them.
I knew this wasn't going to be a cakewalk but I was hoping for a little more success than what I have had so far.
I just spent the past hour comparing the schematic to the pcb and parts installed. I can't seem to find any further errors but then again my eyes are about to fall out of my head from all the staring
I am beginning to suspect my Zeners are either defective from the problems or perhaps were defective right from the wholesaler.
R3, R4, R54 and R57 get pretty hot (100+ F) when the power supply voltage gets to 20Vdc. I can't turn up my variac beyond that or they will start to smoke.
An externally hosted image should be here but it was not working when we last tested it.
I have tested most of the transistors and they all test as new (comparing to my as yet untested AV800 board) so as a precaution I am going to pick up some new Zeners and install them.
An externally hosted image should be here but it was not working when we last tested it.
I knew this wasn't going to be a cakewalk but I was hoping for a little more success than what I have had so far.
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