What wattage do resistors R-44, 55, 59, and 70 need to be. I'd like to place metal films there but am limited to 1/2 watt in size at the local surplus place...... Thanks for any help on this.....
Mark
Mark
Mark, could you post a link to the servicemanual or partslist if you got one?
About the heatsinks, the pictures of other 1.7-projects I've seen has used some smaller heatsinks. That's all I know
About the heatsinks, the pictures of other 1.7-projects I've seen has used some smaller heatsinks. That's all I know
As far as I see, the Vds of Q15 is about 30V and the bias is with about 30mA so that power dissipation = 30 x 0.03 = 1W.
I would summarize power dissipation as follows:
Q15 and Q18: 1W each
Q16, Q17, Q19 and Q20: close to 1W each
Regards
jh
I would summarize power dissipation as follows:
Q15 and Q18: 1W each
Q16, Q17, Q19 and Q20: close to 1W each
Regards
jh
One more question: From looking at the schematic, it seems that both the input and output caps could be a lot smaller than the recommended 10uF/30uF. I've tried calculating the input and output impedances but I'm not sure I have it right 
. What's the minimum value for these caps?
/U.
. What's the minimum value for these caps?/U.
So I assume that 1 watt is ok without sinks on these devices. From photos of others it looks like some use them and some do not.
BTW: Thanks for all the help here!
Mark
BTW: Thanks for all the help here!
Mark
Screw up
I did screw up on some of the resister sizes, sorry. Better to be to big that not big enough. If you let that pre-amp run for a while you'll see why there are heatsinks on the MOSFETs.
It was only my second pre-amp project. The next one will be better.😀
I did screw up on some of the resister sizes, sorry. Better to be to big that not big enough. If you let that pre-amp run for a while you'll see why there are heatsinks on the MOSFETs.
It was only my second pre-amp project. The next one will be better.😀
Mike,
Really... I'm not complaining? I'm very grateful that you sent it. There is not a thing wrong with the boards or anything to complain about at all! If you had more boards I'd love to have several to build up for other people. I decided to take this one to full balanced operation. Had yet to run my 2s in balanced mode at all..... In order to do this there was some re-work that had to be done on both boards. And at the same time I made all the resistors MF's and changed a few others to coencede with the factory version. The ones that I installed were basically the same wattage as yours were...... Regarding the sinks... Some have them and some don't... which has me a bit confused....... So whats up here? Would seem to me that these devices can dissipate a watt free air... or can't they..... I left the sinks on the regulators. If they all need to be on a sink I would consider taking the time to machine a bar of alumnium to thermally connect them all together.
BTW: you ought to hear it in balanced mode🙂
Thanks!
Mark
Really... I'm not complaining? I'm very grateful that you sent it. There is not a thing wrong with the boards or anything to complain about at all! If you had more boards I'd love to have several to build up for other people. I decided to take this one to full balanced operation. Had yet to run my 2s in balanced mode at all..... In order to do this there was some re-work that had to be done on both boards. And at the same time I made all the resistors MF's and changed a few others to coencede with the factory version. The ones that I installed were basically the same wattage as yours were...... Regarding the sinks... Some have them and some don't... which has me a bit confused....... So whats up here? Would seem to me that these devices can dissipate a watt free air... or can't they..... I left the sinks on the regulators. If they all need to be on a sink I would consider taking the time to machine a bar of alumnium to thermally connect them all together.
BTW: you ought to hear it in balanced mode🙂
Thanks!
Mark
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