oxidized contacts in these switches can be deceptive with a meter. the voltage across the meter leads is enough to breakover the oxide, but the signal levels in the tens of millivolts are not. the oxides act like low voltage zener diodes. DPDT switches are what are used here, more specifically ones with no threads on the post (threaded ones won't clear the front panel holes)
Uncle Jed
Well bud, Im getting my amp back together. So far I have both amp boards completely rebuilt, all new components.
Im going to do a final double check of both boards just to be damn sure.
I also re capped the protect and display boards while I was at it.
The only parts I cant find are the moxies, they measure 155k at room temp. Im still looking. If I cant find these do I need to add a resistor to compensate ?
I do have a question for you, I notice in later revisions there is a 1 meg resistor across the input, do you think I should add a 1 meg to the input terminals on the boards ??
Im figuring Ill be able to finish putting her together this weekend.
bob
Well bud, Im getting my amp back together. So far I have both amp boards completely rebuilt, all new components.
Im going to do a final double check of both boards just to be damn sure.
I also re capped the protect and display boards while I was at it.
The only parts I cant find are the moxies, they measure 155k at room temp. Im still looking. If I cant find these do I need to add a resistor to compensate ?
I do have a question for you, I notice in later revisions there is a 1 meg resistor across the input, do you think I should add a 1 meg to the input terminals on the boards ??
Im figuring Ill be able to finish putting her together this weekend.
bob
don't worry if you can't find moxies. all they do is reduce overall amp gain if it begins to overheat. it's a nice feature but not 100% necessary. i'd look them up as thermistors, as that's what they are, if you really need to put them in.
as for the 1M resistor, it's there in the schematic in the owner's manual as R1. i would put it there. if it's there in the owner's manual, and it was put back in in later revs, there must be a reason for it (if for no other reason, to keep C1 from holding any random charge.)
as for the 1M resistor, it's there in the schematic in the owner's manual as R1. i would put it there. if it's there in the owner's manual, and it was put back in in later revs, there must be a reason for it (if for no other reason, to keep C1 from holding any random charge.)
found it.... cantherm ts3 series
http://www.cantherm.com/products/thermistors/cantherm_moxie_ts3.pdf
http://www.cantherm.com/products/thermistors/cantherm_moxie_ts3.pdf
Well Guys got the APT back together, there is a story here.
Carefully fired her up, no major current draw just came to life.
Well the first thing i noticed is the left channel overload led is red, right side came up red then went out.
Started trouble shooting, both channels between 7- 10 mv dc offset, ac 1-2 mv. (noise)
Bias set, amp pulling 250 ma out of the wall.
Powered her back off, connected a signal and speakers.
Offset <7 ac noise zip..
Fired her back up, left led still red both channels playing, right led going green with the signal. impedance mismatch led functioning normally.
Left led still red (overload) ???? or sees some fault.
Pulled fuses from left side amp board, fired amp back up, left led still showing red.
This is telling me that there is nothing wrong with the amp board.
Im thinking the fault must be in the indicator board.
Any ideas ?????
Played the hell out of the amp for a while, she is putting out good power sounds great.
bob
Carefully fired her up, no major current draw just came to life.
Well the first thing i noticed is the left channel overload led is red, right side came up red then went out.
Started trouble shooting, both channels between 7- 10 mv dc offset, ac 1-2 mv. (noise)
Bias set, amp pulling 250 ma out of the wall.
Powered her back off, connected a signal and speakers.
Offset <7 ac noise zip..
Fired her back up, left led still red both channels playing, right led going green with the signal. impedance mismatch led functioning normally.
Left led still red (overload) ???? or sees some fault.
Pulled fuses from left side amp board, fired amp back up, left led still showing red.
This is telling me that there is nothing wrong with the amp board.
Im thinking the fault must be in the indicator board.
Any ideas ?????
Played the hell out of the amp for a while, she is putting out good power sounds great.
bob
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Guys
I figured Id throw this one out there, found another APT amplifier this time with the preamp.
So far found a dirty relay in the preamp, took it out apart cleaned the contacts, back in she plays like a champ dead quiet, clean and clear.
I havent hooked up a turntable yet but all the line level inputs are fine.
The AMP needs a little work, intermittent connection traced to the stereo/mono bridge switch, replacing that. worked switch for a while, the amp is playing well.
Bias set pulling 250 ma out of the wall, offset around 4-7 mv each channel.
Other than that both pre and amplifier working fine !!!!
When it rains it pours. 3 APT 1's, 1 APT preamp.
Just in case the relay for the preamp is an.
IZUMI RY2V-U-DC24 RELAY, DPDT, 3A, 24VDC, PCB MOUNT
bob
I figured Id throw this one out there, found another APT amplifier this time with the preamp.
So far found a dirty relay in the preamp, took it out apart cleaned the contacts, back in she plays like a champ dead quiet, clean and clear.
I havent hooked up a turntable yet but all the line level inputs are fine.
The AMP needs a little work, intermittent connection traced to the stereo/mono bridge switch, replacing that. worked switch for a while, the amp is playing well.
Bias set pulling 250 ma out of the wall, offset around 4-7 mv each channel.
Other than that both pre and amplifier working fine !!!!
When it rains it pours. 3 APT 1's, 1 APT preamp.
Just in case the relay for the preamp is an.
IZUMI RY2V-U-DC24 RELAY, DPDT, 3A, 24VDC, PCB MOUNT
bob
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probably a bad op amp on the display board. check the transistors there while you're at it. make sure there's a piece of plastic or fish paper (the same kind of slate impregnated cardboard they used to cover the power transformer) between the display board and the left channel amp module. if the display board hits the fuse holder while the supply caps are charged it can damage the op amp (most likely the left one). this can happen in shipping or if the amp gets dropped. after the problem was discovered, APT made a piece of fish paper that covered the back of the display board and got screwed in with the display board mounting screws.
once again the instant notifier didn't email me.... good thing i thought to check back here....
once again the instant notifier didn't email me.... good thing i thought to check back here....
Thanks Jed
I was thinking the same thing, Ill go on and change out the opamps, I might as well swap out transistors too, I got prolly 50 of that type.
Other than that the amp sounds pretty darn good. hell most of it is new.
bob
Ill keep an eye out for you. Im thinking there may be quite a few around here. a local dealer sold them new.
bob
Swapped out both op amps, and the 3 2N3904's on the display board. No change.
Im wondering if I might have a squirrely opamp on the amp board, luckily I socketed all the opamps.
bob
Guys
I found a pretty cool solution to protect the display board in the APT 1 amplifier.
As Uncle Jed mentioned in an earlier post there is a possibility that the fuse clip closest to the display board could make contact.
I found a cheapskate solution, I used a soft plastic cassette tape case, just cut a large corner out of the deeper of the case, It covers the entire display board, with about 1/2 inch lip on two sides. Slips over and completely protects the back side of the display board.
bob
I found a pretty cool solution to protect the display board in the APT 1 amplifier.
As Uncle Jed mentioned in an earlier post there is a possibility that the fuse clip closest to the display board could make contact.
I found a cheapskate solution, I used a soft plastic cassette tape case, just cut a large corner out of the deeper of the case, It covers the entire display board, with about 1/2 inch lip on two sides. Slips over and completely protects the back side of the display board.
bob
Good point, didn't think about UL. need to find fish paper or phenolic.not exactly UL approved materials, but it will work....
bob
i'm still in the industry, and i hear the horror stories.... house fires started by resistors that should have been flameproof, but were replaced by regular resistors, etc, the wrong speaker cables used in somebody's ceiling, etc...for hobbyist/diy stuff it's not a big deal, but i am real careful about what i put in a piece of consumer gear. don't want an army of "ambulance chasers" after me if something happens to go wrong.
soft plastics are flammable, and it doesn't matter if they're in contact with line voltage. if it can sustain a flame or can decompose and release flammable gasses when heated, don;t use it. at least not in consumer equipment. lawyers love that kind of stuff, it pays for their expensive cars. such plastics (like LDPE) are almost nonexistent in consumer equipment for just that reason. that's also why circuit boards are now made of only a few types of materials, they have to pass a flame retarding test.