FET "Grinder"
- Thread starter Gustav
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kante1603
Well-known member
Yes ;Djicama said:
Rocinante
Well-known member
Alright I give up. So I've read a good deal of the threads via the Meta thread regarding the circuit but I guess I just need a more specific answer. So I have signal. I have my 30 and -10. My Psu appears to be working fine. I am using the Hairball 25-0-25 at 30v to power my Phat Phet as well as an Edcor xs1100 with a Don Audio adapter for the output xfmr. Okay so I can trace the signal coming in and at the input pot am getting a good signal BUT at the next 27k resistor (I believe where it travels to next??) and right before bf245a it's gone. Nada. I get nothing also anywhere else. So is it safe to assume I just have a bad Fet? Is there somewhere else I can look? Reading this little guideline written by Mark Burnley where he gives a pretty awesome and detailed breakdown of tracing the 1176's signal path;
http://groupdiy.com/index.php?topic=4481.0
it feels like the Fet must be what's wrong.
Now considering that bf245a's are nearly extinct (at least in the states) I guess it's a pair of 1N5257's I am gonna need but before I go through the trouble of ordering them (then the damn 5 day wait for just two Fet's!!!) I was just wondering if there is anything else I can check first?
Thanks
D
http://groupdiy.com/index.php?topic=4481.0
it feels like the Fet must be what's wrong.
Now considering that bf245a's are nearly extinct (at least in the states) I guess it's a pair of 1N5257's I am gonna need but before I go through the trouble of ordering them (then the damn 5 day wait for just two Fet's!!!) I was just wondering if there is anything else I can check first?
Thanks
D
Rocinante
Well-known member
Gustav; thank you. Will do. Always the man.
Cheers
Dylan
Cheers
Dylan
Ok now I had time to continue with the project and trying to calibrate it which I couldn't because the meter I have it looks like the one you will need to solder an Bridge.
Can I use this little guy in the picture? http://chatel91.com/144-large/w08m.jpg , it's a "W08M" and if I the answer is positive, how should I should I do it?
I've been looking for pictures but couldn't find anything
Thanks for the help
Can I use this little guy in the picture? http://chatel91.com/144-large/w08m.jpg , it's a "W08M" and if I the answer is positive, how should I should I do it?
I've been looking for pictures but couldn't find anything
Thanks for the help
kante1603
Well-known member
Don't know if a roundbridge rectifier will do this job properly,it's normally used on a psu.
Best to follow the recommendations here and go for germanium or Schottky diodes like BAT85 etc.Have used them often in my compressor builds from JLM.,and they are less than 8 Euro cent a piece when bought as singles.
The shown meter is a standard B*******r type,so the same as mine.
Hope to have helped,
Udo.
Best to follow the recommendations here and go for germanium or Schottky diodes like BAT85 etc.Have used them often in my compressor builds from JLM.,and they are less than 8 Euro cent a piece when bought as singles.
The shown meter is a standard B*******r type,so the same as mine.
Hope to have helped,
Udo.
kante1603 said:
Thanks for the answer, tomorrow i will go to get some of those, now I only have 4148, uf4001 and 1n4004 :-\
So i need 8 diodes for 2 meters? but Im still confused how can I solder them before the meter ???
In the mean time am I able to calibrate the Qbias with a multimeter to know if the unit behave as it should be??
kante1603
Well-known member
Taken from Gustav's homepage:jicama said:
https://pcbgrinder.com/download/Data_Sheets/Bridge.jpg
Udo.
kante1603
Well-known member
Yes,with the correct diodes (germanium or Schottky) of course,
Udo.
Udo.
kante1603
Well-known member
They will definetely work,maybe even your round rectifier will.....somehow and at high levels.jicama said:
Germanium and Schottky do it better when it comes to low level readings and accuracy.
Udo.
kante1603 said:
Ok got thanks for the advise Ill get those for accuracy readings
, for the moment I soldered 4148 for the Q Bias adjustment, and found a couple of strange things, I can't really hear compression, input switch is making some pops and regulators on the psu are getting very hot.I'm only using 1 PSU to feed both boards and the 2 lamps from the meters I posted before which needs 6v to 12v,on the resistance before the lamps I put 360R to drop the V, do you think is why the regulators from the psu are super hot?
Thanks
Thanks
kante1603
Well-known member
Sorry that I can't help you in this case because I haven't built these guys (yet).jicama said:
So I don't know what the expected power consumption is for one board,what kind of psu it is,the transformer specs etc.
I would start measuring the voltages as usual.
Then start to sort things out.If the psu is not on the main board start measuring output voltages from the naked psu.
Then only connect one(!) board,no lights for the meter attached.
Do it with both boards and see if something changes.
Then run them in parallel as you did before,but still without lights.
In case the vu meter lights are bulb tubes or normal lamps be aware that these are really power suckers.
I always swap them out for a nice led.
Regulators start getting hot under several circumstances,wether the circuits draw too much current,wrong input voltage/wrong transformer etc.
For everything else Gustav or builders who have done them should chime in to get some more detailled specs.
Best,
Udo.
kante1603 said:
Hey there,
I've disconnected the meter lamps from the PSU with the regulators are still hot, the LM337 a bit more, I will try to run 1 board from the PSU to see if something change, voltage from PSU are good will continue the V measures on the board, do you know where should I look for non compression issues?
Thanks
Rocinante
Well-known member
Damn. It wasn't the BF245 apparently. Thank you Gustav for sending me those (as quickly as you did I might add), your integrity is as respectable as it is genuine.
Okay so I can follow the circuit through the input stage to the input pot then right up unto the 27k resistor (next to the 220nf cap in the 'preamp' section) and on one side of the resistor (closest to the input pot) I have a signal and on the other side nothing.
Originally I had believed that the bf245 that follows it (27k resistor) was at fault but after having replaced it I now know that it is unfortunately something else. In vain I decided to replace the 27k R with a 24.9k (that's close enough right?) but it made no difference whatsoever. One side I get signal the other side static.
Okay so I can follow the circuit through the input stage to the input pot then right up unto the 27k resistor (next to the 220nf cap in the 'preamp' section) and on one side of the resistor (closest to the input pot) I have a signal and on the other side nothing.
Originally I had believed that the bf245 that follows it (27k resistor) was at fault but after having replaced it I now know that it is unfortunately something else. In vain I decided to replace the 27k R with a 24.9k (that's close enough right?) but it made no difference whatsoever. One side I get signal the other side static.
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