nashou
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Post by nashou on Feb 8, 2016 11:48:45 GMT -5
I'm working on a A-1 that had the Disc button constantly iluminated. I opened it up and cleaned all the switches with cleaner and re assembled the amp. On trying to power up the power switch does not "catch" to keep the amp on. I have to hold the switch down for the amp to to turn on and allow the speker relay to click. At least the Disc switch goes off. Here is a pic of the part. I can't make out the manufacturer name or symbol. I have been looking for a similar part on Mouser but I dont know what type of switch this is. Dpst? Spst? etc and if its an ON-OFF, or ON-ON they ask you this when doing a search. I do know from the service manual its a 15 amp 125 v part.  I found out its an alps part on Audiokarma , but they no longer make it. I found some that look similar. This switch pushes in and pops out again but the unit stays on, then it pushes in again and turns off. It was working before I cleaned it. Not sure what type this is called. I have seen phrases and momentary latched , momentary etc. what I am asking is what is the type of switch I am looking for that spring out after each push but leave the unit on or off after and returns to its original location. I found this on Digikey and looks similar. but not as much current. www.digikey.com/product-search/en?mpart=P197EESB&v=141Aslo I found these on Ebay that look close. www.ebay.com/itm/10-POWER-SWITCHES-NEW-PUSH-LOCK-TYPE-BY-ALPS-UL-APPROVED-RATED-TV-3-MANY-UNITS-/381484756736?hash=item58d2436f00:g:Nl4AAOSwnH1WYcAkBut again not sure of power rating. Or is there something I did when cleaning it with contact cleaner lubricant that might have it work again if i clean it with some denatured alcohol? nashou |
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Post by mastertech on Feb 9, 2016 9:07:15 GMT -5
I would try cleaning it with WD40. That is what I use all the time. Soak it up good so the crap runs run of it.
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nashou
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Post by nashou on Feb 9, 2016 10:07:36 GMT -5
I would try cleaning it with WD40. That is what I use all the time. Soak it up good so the crap runs run of it. The thing is it worked before I used the radio shack contact cleaner . I didn't have any WD-40 on hand. I know you love it for cleaning contacts switches and trimpots. I ordered the switch from Digikey along with caps for the PS board . I'll try the WD-40 too. Nashou |
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nashou
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Post by nashou on Feb 9, 2016 13:21:49 GMT -5
Well the WD 40 didn't help. I even smacked it with a small ball peen hammer to maybe break free what ever it is that is preventing the switch to "latch" . My order shipped out so we'll see if the new switch is the same type. only a 2 $ part. I got a pic of the back sticker on my switch too using a mirror   |
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nashou
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Post by nashou on Feb 13, 2016 21:06:58 GMT -5
I installed the new Switch and it worked perfectly.    I also took the old switch part just to see what was up with it. Turns out to be a piece or part was in there and must have not allowed the leaf spring to keep contact made. So I removed that part and put it back together and it seems that it works now. But I am leaving the new part in for now. |
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nashou
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Post by nashou on Feb 14, 2016 22:18:23 GMT -5
Ok So the switch works, I got it all back together and tested it with audio from my iPhone and first the right Speaker out then the left.
Right is fine, left is scratchy. When I had it apart i cleaned all controls and switches. Also I tested right at a fairly high volume level and
it was nice and clean, left I tried it was scratchy all the way up the range and then the speaker relay protect kicked in at the same high level
as when i tested the right. Will the distortion kick in this protection?
I don't think its the volume. I also tested all inputs. I have not check Phono as I gave my test player to my nephew.
Where should I look. Nashou
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Post by mastertech on Feb 15, 2016 11:41:15 GMT -5
You really should be testing with more then 1 source and also different source cables and also on different inputs.
You should also test the headphone output and preamp out (if possible)before looking for an internal problem. These tests can also help narrow down where the problem may be if it does end up being internal.
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nashou
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Post by nashou on Feb 15, 2016 12:53:14 GMT -5
You really should be testing with more then 1 source and also different source cables and also on different inputs. You should also test the headphone output and preamp out (if possible)before looking for an internal problem. These tests can also help narrow down where the problem may be if it does end up being internal. Before I went to bed I did test with the head phones and it was there as well. So that leads me to the volume pot again. I'll need to give it some WD-40 this time. Before it was just the Radio Shack cleaner lubricant. Nashou |
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nashou
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Post by nashou on Feb 17, 2016 20:18:30 GMT -5
Ok I tested again on different inputs and the same. I tested the cables on my other A1 on all inputs and it works fine. So this 1/8 phono to RCA plugs works fine.
I really shot a lot of WD 40 in the volume and turned it about 50 times. It was pouring out every hole in the Pot. Also the pot has two screwed and comes apart.
SO I removed the screws( still soldered to PCB) and the box was able to open a bit so I squirted more WD 40 into the split box and turned it another 50 times.
Then put screws back in and tried one more time. Same thing. ugh. I then proceeded tot he Speaker switch, and the selector switches . Nothing.
I was thinking of trying to by pass the volume control for the left channel only and use a source with its own volume control( i have been using my iPhone) .
Is there a way to do this safely? I am going to look at the schematics now.
Nashou
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Post by mastertech on Feb 18, 2016 11:57:10 GMT -5
At this point I would start probing locations on the good and bad channel and comparing the 2. This can be done with the scope or the audio device that I have talked about before in the past with another receiver and speaker/headphones. This would be done, "before" the amp section, not after the siganl enters the amp section. Well the scope can be used in the amp section but not the receiver device.
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nashou
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Tech in Training.....
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Post by nashou on Feb 18, 2016 13:01:29 GMT -5
At this point I would start probing locations on the good and bad channel and comparing the 2. This can be done with the scope or the audio device that I have talked about before in the past with another receiver and speaker/headphones. This would be done, "before" the amp section, not after the siganl enters the amp section. Well the scope can be used in the amp section but not the receiver device.  Oh, And I DID forget to check the preamp outs into another amp. Let me try that as well. I have an LCR meter that does send out a 1khz tone. I found that out when it was connected directly to my KEF speaker I repaired and the speaker played the tone. Can I use this on the Three inputs of the A1 and also on MM phono input( the only inputs I did not test as I have no turntable in the shop and i have a test tone LP I can use too! Waitin on a head shell for my test TT) ? It sends the tone when measuring any of the parameters L, C Z or R. I was also going to remove the POT and take it apart to clean it better or should we wait? Nashou |
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Post by mastertech on Feb 18, 2016 13:04:26 GMT -5
I would wait on taking that pot apart. Let me know how you make out with the preamp out test.
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nashou
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Post by nashou on Feb 18, 2016 13:16:30 GMT -5
I would wait on taking that pot apart. Let me know how you make out with the preamp out test. Ok That will be later today, At work now. Finally slowed down enough for me to waste time in the office PS: This seams to be more of a challenge than the other recivers where we are just trying to get them to work or output sound. Having this work but not optimally appears to be more challenging . Nashou |
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nashou
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Tech in Training.....
Posts: 1,239
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Post by nashou on Feb 18, 2016 19:31:55 GMT -5
Ok Here is some interesting observations if i can get them all right, I should have taken notes I am only using one speaker , switching it between left and right. With pre amp out to a Yamaha TX-sr707's using the CD input i get a much cleaner left channel. Right channel also good. Now on the A1, the volume control has a dual shaft volume control. How this works is the center shaft is the left balance and the outer shaft is the right balance. To only turn the left channel you have to hold the back part of the volume knob and turn the face of the volume knob to increase volume for left, and the opposite, tuning back of knob, to increase right volume . So having explained how this amp works I noticed if I Hold the left "balance" to 0 and increase the right volume with only the left speaker connected( this is pre amp out not internal amp) it increases Bass on left channel ! and visa versa. Now If i use the A1's amp or speaker outs this does not happen, If this is normal I have no Idea as I never tried it before. Aslo , if I press the mono control testing Pre amp out the sound goes way down , on both channels. If I use the A1's speaker outs this does not happen. not sure if this is normal once again. But i would think not. I also re checked the left channel through the A1 speaker out and it was much more distortion than with the Pre outs. |
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Post by mastertech on Feb 18, 2016 20:01:32 GMT -5
You have to realize that the audio signal goes through almost every switch on that unit, even if it is selected as "off". So dirty contacts in any of those switches can give a static or distorted signal. Try WD "all" switches and working them in and out and see if anything changes.
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