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Old 26th January 2011, 06:08 AM   #1
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Default Can anyone help with JVC JAS22

Hi I was just wondering if someone can help with a problem I am having with this amp, it has over time developed a crackling volume control.
I know this is a common fault with amplifiers of this age but I would like too replace the pot if possible, rather that using contact cleaner, off course I’m not very knowledgeable about these things which is why I came here for help. I am just not sure what part to get is there an exact replacement the label on the pot says qvz-1219-005,m250kohmbx2,583L A. If it is not possible too get this part or similar and I have to use contact cleaner which do you recommend? Thank you..

Service Manual free download,schematics,datasheets,eeprom bins,pcb,repair info for test equipment and electronics

Service Manual free download,schematics,datasheets,eeprom bins,pcb,repair info for test equipment and electronics
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Old 26th January 2011, 06:34 PM   #2
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Wouldn't recommend 'Super Servisol 10', it's useless.
If you can get Philips 390CCS then that was quite good.
The Americans had the best stuff, it was called 'Blue Stuff' but probably not available any more, perhaps our American pals can tell us?
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Old 26th January 2011, 09:11 PM   #3
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Thanks toprepairman how about this stuff Caig Deoxit D5 Contact Cleaner a lot of people say it's quite good. But at twenty pound a can it's a bit pricy, probably more than the replacement part might cost.
Is there no one here that can tell me the part I need.
The amp was made in 1978 but has an amazing transparent sound and good stereo imagery.
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Old 27th January 2011, 11:54 AM   #4
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Never seen/used Deoxit D5 so can't comment on that one.
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Old 27th January 2011, 12:01 PM   #5
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Depending on the internal arrangement it may be possible to fit an Alps Blue.
Can't remember if the original was a special, in which case it is unlikely you'd get another.
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Old 27th January 2011, 05:02 PM   #6
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Looking at it again it's a dual pot with six lugs at the bottom and two at the top (one on each barrel) probably for the loudness switch. The bx2 at the end of the number might mean dual, does the B mean linear?
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Old 28th January 2011, 07:07 AM   #7
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It'll be a log pot, and you're correct with the two extra lugs being for 'loudness'.
Most Alps blues also have the extra pin connections for loudness so you should be Ok there.
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Old 6th February 2011, 05:09 PM   #8
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I really appretiate your help toprepair man, I'm almost ashamed to say but after spraying with some servisol super 10 switch contact cleaner there is no more crackle at all. but am having trouble getting the centre voltage to balance up even after spraying them it has no effect the reading seems to be all over the place the manual suggest to adjust them below +/- 10 mv but at switch on one channel reads 68mv then climbs down after 15 mins then up to - 28 the slightest adjustment tends to make them move alot do i need to replace these. The manual says these are 220ohm 0.15 W Variable carbon R311 and R312.
What would be a high quality replacment, I heard ceramic are good but have no idea which ones to buy. Thanks.
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Old 7th February 2011, 12:06 PM   #9
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No probs with the servisol 10, if it worked then that's just fine.
You should be Ok with any replacement trimmers, the cermet ones will certainly work fine. You're unlikely to get something to fit right in but if you extend the pins with something like 22 gauge wire then that will work.
Regards
Henry

Ps. If you're in the south east, try visiting then Audiojumble at Tonbridge this Sunday.
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Old 7th February 2011, 12:28 PM   #10
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Those trim pots are usually very reliable.
Check boards for crook solder joints especially on the output ic's pins and throughout the driver stage.
My preference is to just blanket resolder the power amp stages, also resolder the regulator stages.
This has cured thousands of amplifiers for me with 100% reliability.

Eric.
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