Mpsa56
> I have not changed the Tr's to MPSA56 yet. These transistors have disappeared in this part of the world. Not even Farnell can source them from its Singaporean or UK warehouse!!!
www.reichelt.de, 0.09 cent (HK$1) per piece.
They unfortunately have a minimum order of 100 Euro for overseas orders. I can order some next time when I order from them, if you want. Post to HK at cost. No guarantee for source of the transistors unfortunately; always have been the case for Reichelt.
Another source :
http://fibra-brandt.com/ @ 0.10 cent each.
He will sell to anyone anywhere. Your bank draft charges and post will cost more than the transistors, unless you want 100+.
Patrick
> I have not changed the Tr's to MPSA56 yet. These transistors have disappeared in this part of the world. Not even Farnell can source them from its Singaporean or UK warehouse!!!
www.reichelt.de, 0.09 cent (HK$1) per piece.
They unfortunately have a minimum order of 100 Euro for overseas orders. I can order some next time when I order from them, if you want. Post to HK at cost. No guarantee for source of the transistors unfortunately; always have been the case for Reichelt.
Another source :
http://fibra-brandt.com/ @ 0.10 cent each.
He will sell to anyone anywhere. Your bank draft charges and post will cost more than the transistors, unless you want 100+.
Patrick
Re: Mpsa56
Thanks for all the generous gestures.
I have just arranged delivery from Newark in the States through my local Farnell. The cost is ~$3.7US for 25 pieces. No minimum charge. No delivery cost. The TR's are Fairchild, though.
BTW, how to attach photos?? Is it by using the "Attach file" option?? But I cannot see the file is attached in the "Preview Reply" Mode???
CY
bremen nacht said:
EUVL said:
www.reichelt.de, 0.09 cent (HK$1) per piece.
They unfortunately have a minimum order of 100 Euro for overseas orders. I can order some next time when I order from them, if you want. Post to HK at cost. No guarantee for source of the transistors unfortunately; always have been the case for Reichelt.
Another source :
http://fibra-brandt.com/ @ 0.10 cent each.
He will sell to anyone anywhere. Your bank draft charges and post will cost more than the transistors, unless you want 100+.
Thanks for all the generous gestures.
I have just arranged delivery from Newark in the States through my local Farnell. The cost is ~$3.7US for 25 pieces. No minimum charge. No delivery cost. The TR's are Fairchild, though.
BTW, how to attach photos?? Is it by using the "Attach file" option?? But I cannot see the file is attached in the "Preview Reply" Mode???
CY
Hello again.
I built a JHL 10 watt amp using the regulated PSU 338k and at first I had the feedback cap removed with the D.C. compensation transistors installed. First time I got the amp working I had 7. volts dc at the output but I guess that I adjusted the dc away.
Well after several on off cycles I adjusted the dc to around 150 mv cold and 25 mv when the amp was hot with 2 amps Iq.
I am running 24 v rails and my transformer is 22-0-22 180va.
One day I turned the amp on and I had 7.volts D.C. on the output and the d.c adjustment was nonefective.
I checked Q5 and Q6. They both seemed fine and so I checked the rest of the tranies no problems.
I installed the feedback cap c4 and the d.c. was now adjustable but when cold I have around 800mv d.c. at output and 10mv. d.c. when hot.
If I short across the feedback cap I get 7. volts d.c.
I do have a scope and I cannot see any apparent oscillations.
Things also seem to change when the amp is hot. At one point I adjusted the output d.c. to 200mv as that was as far as I could adjust the d.c. and left the amp. As it heated up more the d.c. suddenly when to 24vd.c. I then was able too adjust the vd.c.to
bawlingnear 10mv d.c.
I have no idea what is going on .
Thanks Steve.
I built a JHL 10 watt amp using the regulated PSU 338k and at first I had the feedback cap removed with the D.C. compensation transistors installed. First time I got the amp working I had 7. volts dc at the output but I guess that I adjusted the dc away.
Well after several on off cycles I adjusted the dc to around 150 mv cold and 25 mv when the amp was hot with 2 amps Iq.
I am running 24 v rails and my transformer is 22-0-22 180va.
One day I turned the amp on and I had 7.volts D.C. on the output and the d.c adjustment was nonefective.
I checked Q5 and Q6. They both seemed fine and so I checked the rest of the tranies no problems.
I installed the feedback cap c4 and the d.c. was now adjustable but when cold I have around 800mv d.c. at output and 10mv. d.c. when hot.
If I short across the feedback cap I get 7. volts d.c.
I do have a scope and I cannot see any apparent oscillations.
Things also seem to change when the amp is hot. At one point I adjusted the output d.c. to 200mv as that was as far as I could adjust the d.c. and left the amp. As it heated up more the d.c. suddenly when to 24vd.c. I then was able too adjust the vd.c.to
bawlingnear 10mv d.c.
I have no idea what is going on .
Thanks Steve.
Steve,
I am not sure I can really help you with your problem. Yours is more weir than mine.
I had for some time when prototyping with my JLH had the output offset stayed as high as the rail. Well, the reason was wrong intial setting of VR2 in its stock form causing many Tr's to vaporise when powered on. I replaced VR2 as I felt that the initial portion of the track had burnt out. Your problem is not quite like mine. VR2 may not be the issue but is worth to check.
I also feel that Q4 should serve a prime role to control the output offset. Your probem seems to be that the offset is controllable when R6 is removed (from a dc point of view) but is not controllable when R6 is inserted to form the potential divider (R8 and R6). I would suspect whether Q4 is still functioning with its HIGH gain. I would also suspect and check whether R2 is properly soldered to ground.
CY
serosmaness said:
I am not sure I can really help you with your problem. Yours is more weir than mine.
I had for some time when prototyping with my JLH had the output offset stayed as high as the rail. Well, the reason was wrong intial setting of VR2 in its stock form causing many Tr's to vaporise when powered on. I replaced VR2 as I felt that the initial portion of the track had burnt out. Your problem is not quite like mine. VR2 may not be the issue but is worth to check.
I also feel that Q4 should serve a prime role to control the output offset. Your probem seems to be that the offset is controllable when R6 is removed (from a dc point of view) but is not controllable when R6 is inserted to form the potential divider (R8 and R6). I would suspect whether Q4 is still functioning with its HIGH gain. I would also suspect and check whether R2 is properly soldered to ground.
CY
Well now I have the amp to 10mv dc on the output but only after it heats up for a couple of hours.
When I first turn on the amp I get 900mv dc on the output.
I am thinking a cold soldering joint but I have not opened the amp up as I am useing it.
Will 1 vdc damage my speakers?
Thanks Steve
When I first turn on the amp I get 900mv dc on the output.
I am thinking a cold soldering joint but I have not opened the amp up as I am useing it.
Will 1 vdc damage my speakers?
Thanks Steve
Thanks. These are my first attempt at building the entire amp without using a manufactured case.
There is a local hardwood floor manufacture that sells their remnants as firewood.
I do not know what type of wood this is but it is very hard and heavy.
I will post photos of the inside of one the amps tomorrow.
Serosmaness
There is a local hardwood floor manufacture that sells their remnants as firewood.
I do not know what type of wood this is but it is very hard and heavy.
I will post photos of the inside of one the amps tomorrow.
Serosmaness
Just for info...
There is a type of wood that is time proof. I am writting this for the info of some non tropical res.
It is called TEAK wood and is tropical.
(ROSE wood is also good, but black in color)
This wood is so good that even if u throw/plant in the earth, nothing happens to it for generations. U should avoid using the white non textured part, like lower part in top amp of Serosmaness.
Gajanan Phadte
There is a type of wood that is time proof. I am writting this for the info of some non tropical res.
It is called TEAK wood and is tropical.
(ROSE wood is also good, but black in color)
This wood is so good that even if u throw/plant in the earth, nothing happens to it for generations. U should avoid using the white non textured part, like lower part in top amp of Serosmaness.
Gajanan Phadte
Re: fin alignment
not so much cheap as convenient!
It's just that thermal resistance is generally specified with fins vertical in free air, and I was wondering how much to derate when using the same heatsink in different orientations. I emailed Marston to ask about using heatsinks on top of enclosures (ie heatsink 'on its back', fins pointing skywards) and they said it made virtually no difference if the fins were less than 300mm long. I didn't ask about horizontal fins.
mikelm said:
not so much cheap as convenient!
It's just that thermal resistance is generally specified with fins vertical in free air, and I was wondering how much to derate when using the same heatsink in different orientations. I emailed Marston to ask about using heatsinks on top of enclosures (ie heatsink 'on its back', fins pointing skywards) and they said it made virtually no difference if the fins were less than 300mm long. I didn't ask about horizontal fins.
I am Married and so I doubt that my wife would approve of the heatsinks standing upright as it is she claims that there are to many electronic devices to turn on.
P.S. My daughter is 3 years old and asks if I am ever finished working on my amplifiers and she knows the word "amplifier".
Steve
P.S. My daughter is 3 years old and asks if I am ever finished working on my amplifiers and she knows the word "amplifier".
Steve