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Post by Deleted on Aug 1, 2013 1:56:19 GMT
I will let you try that. It nearly made my ears bleed that other time . Regards Alex
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Post by Deleted on Aug 1, 2013 14:36:38 GMT
Cheers Greg.
I didn't get my listening session at home last night as it was one of those "everything sounds crap" moments.
Oh well, another day...
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Post by Deleted on Aug 2, 2013 0:51:59 GMT
Ooooooh, Alex! Digi psu done. I never really got the same bass weight from the SC DAC that I do from the Amanero/PK combo, though other aspects were superior. With this mod, enter the bass, nice tuneful, controlled, precise and digs deep if it's there. Did a tidier job this time. I can't wait to get it home and try on a better coaxial signal. Hi Chris I just realised that on this PCB, you are still using a 100 ohm PW5 resistor to drop the voltage to the 7805 down a bit,in order to reduce how hot the 7805 runs. With my PSU I am using a 5.1V 5W Zener there instead to reduce the voltage. This was supplied with the PSUs for the Studio Series Preamp. This would also help a little with any load variations. On the +5V supply for the DAC PCB I have been able to insert a 7812 voltage regulator in between the filter capacitors and the input to the 7805. This gives an extra stage of noise rejection. On an earlier revision of this PSU PCB, all you had to do was drill an additional hole near the location of the 100 ohm PW5 resistor and then bend the centre ( earth) lead of the 7812 across to a nearby earth point. With later Jaycar revisions of this PCB it isn't that easy however. It could be worth a look though ? I also intend to do similar withy the +5V digital supply, where the 5.1V Zener is presently. Kind Regards Alex P.S. I obtained another KC5418 PSU kit from Jaycar earlier today, and all I need to do to add a 7812 ,is drill just one additional hole in the PCB. There is already a vacant hole where the earth (centre) leg of the 7812 can go. I may have to fiddle around with the orientation of the heatsink for the LM317T.
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Post by Deleted on Aug 2, 2013 11:10:26 GMT
Hi Alex. Like this? Ta
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Post by Deleted on Aug 2, 2013 11:33:33 GMT
Hi Alex. Like this? Ta Hi Chris Yes. Simple , isn't it ? I can't guarantee there will be an audible improvement, but it should be better technically.My DAC PCB's PSU has been like this as long as I can remember. I just never got around to doing the same for the Digital PSU PCB. I am presently assembling a new PSU PCB with the SM diodes as per the one supplying +-15V and +5V to the DAC.The idea is that I can just swap Digital area PSU PCBs and see what happens. Nothing ventured = Nothing gained ? Kind Regards Alex
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Post by Deleted on Aug 3, 2013 2:32:55 GMT
Modified S.C. PSU +-15V and +5VSurface Mount diodes (ES1D) fitted to bridge rectifier section, and a 7812 voltage regulator pre-filters the +5V supply, as well as reducing the temperature of the 7805 voltage regulator. The heatsink for the LM317T, which is near the added 7812 has been turned around . D1 and D3 have been fitted underneath the PCB.D6 and D8 were also replaced, mainly because I needed the practice with these devices on a PCB not designed for SMD components. Uploaded with ImageShack.us
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Post by Deleted on Aug 4, 2013 3:00:57 GMT
A word of warning Re 7805 voltage regulators.
Make sure that you check the voltage out from a 7805 VR before connecting up it's output. If the voltage is a little high, then try it with a dummy load of say 1K ohms or lower. I had to replace 2 new 7805s this morning that were too high a voltage output. The lowest voltage one was 5.274V, and that was with a load of 5mA. The voltage out did not change , with or without the 1K resistor. Both of these were marked ON , which is normally a highly reputable supplier. I wonder if these 2 from Jaycar were fakes ? I then replaced the 7805 with an unused 7805 from a different manufacturer, and the output was then 5.032V The input was 11.82V from a 7812 in series with the 7805.
Alex
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Post by Deleted on Aug 6, 2013 7:41:14 GMT
I just tried the 1st of those “ON” 7805s in a simple S.C. PSU PCB for dual fixed regs The output is 5.434V into o/c and 5.412V into a 470 ohm load. I will be checking with Jaycar HQ to see if these are from the same batch as theirs. Alex
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Post by Deleted on Aug 6, 2013 22:56:57 GMT
My 7805s are also "ON". The psu kits are not recent stock so I'll give mine a check when I get home a little later on.
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Post by Deleted on Aug 6, 2013 23:51:55 GMT
My 7805s are also "ON". The psu kits are not recent stock so I'll give mine a check when I get home a little later on. Hi Chris I have just returned from Jaycar HQ. The store manager said he would email the upper managers, but insisted that they would not come down to talk to customers. I did however leave a small older style PSU PCB with them where I had transferred the worst of the 2 devices for easy testing. Although another PSU kit on the shelf also had an ON MC7805CT, it was from a different batch number. I am NOT a happy bunny ! Kind Regards Alex
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Post by Deleted on Aug 7, 2013 0:33:46 GMT
Hi Alex,
Did they replace the bad regs?
The upper management probably don't know any technical anyway.
Regards
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Post by Deleted on Aug 7, 2013 0:45:20 GMT
Hi Alex, Did they replace the bad regs? The upper management probably don't know any technical anyway. Regards Hi Greg I didn't ask for replacements. I just wanted the bloody store manager to make sure this was followed up, and not just via an email that may be missed or ignored. I had hoped to keep this in house, but after that I emailed Leo Simpson with my findings, and mentioned that I had left the faulty devices with Jaycar to follow up. I was tempted to try and contact Garry Johnston who would remember me from Sussex St. days, when he personally delivered an amplifier kit to me at Chatswood T.E. . Kind Regards Alex
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