| reddish75 |
hi, i have a slight problem the volume pot on my pioneer a400 has gone faulty, the only problem is this pot incorporates balance control as well!
does anyone know of a replacement or could a just put a regular volume pot on in place, and just omit the balance part. does anyonehave any experence with this? or where on the pcb i should solder too?
thanks
chris |
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| rabbitz |
Here's a service manual for the A400X which should use the same pot. It's a linear pot that fake lawed with a resistor to give a log taper so a normal log pot would not work unless you remove the resistors (can't remember if a link is required in these positions).
http://www.audio-circuit.dk/Schemat...400X_int_sm.pdf
How do you know the pot's faulty as mine was a bit scratchy and just gave it a clean and it's now fine. |
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| homemodder |
| WD40 does wonders yes. |
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| reddish75 |
| yes i tried to clean it with switch cleaner, however somehow this pot has a crack in the circuit board, hence needing to purchace a new pot. is there any way to fix the carbon track? |
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| EchoWars |
WD-40? Is that a joke?
reddish, you can try conductive paint on the crack to bridge the disconnected sections together. |
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| homemodder |
Absolutely no joke, read the uses, repel moisture, luberification of moving parts, cleaning, protection against oxidation and corrosion, many more. Most excellent British product.
Conductive paint can work yes, but i think its better replacing that pot, can you take a pick of it, maybe can suggest a replacement. I think Alps has one with built in balance control. |
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| EchoWars |
| WD-40 is horrid stuff to use on a potentiometer. Period. I've had to replace dozens of pots that were sprayed with the stuff and destroyed. |
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| sakis |
| quote: | Originally posted by homemodder
Absolutely no joke, read the uses, repel moisture, luberification of moving parts, cleaning, protection against oxidation and corrosion, many more. Most excellent British product.
Conductive paint can work yes, but i think its better replacing that pot, can you take a pick of it, maybe can suggest a replacement. I think Alps has one with built in balance control. |
homemodder yes!!!!!! WD40 is out is simply out of the question ..... forget everything else and just thing the oil leftovers inside your pot ....except that they work like toxic to plastics also as a magnet to dust .....
every pot sprayed with WD40 will fail in the future
| quote: | Originally posted by EchoWars
WD-40 is horrid stuff to use on a potentiometer. Period. I've had to replace dozens of pots that were sprayed with the stuff and destroyed. |
Echo wars is very right .....many times i had to do the same |
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| sakis |
you may post a picture of the pot there is a good chance that i have an original one but i am not shure if the ones i have has also loudness pins on it also
you may e mail me if you want
( local pioneer repair shop is went out of job and i have acces to many strange parts ) |
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| homemodder |
Its not really an oil, spray some on your hand and let it dry and see if there is any oily residue. I have repaired hundreds of pots in amps, in particular Rotels which some use Alps pots, my customers are happy, never one returned for the same problem with a pot. I only repair friends or their friends equipment, if anyone of them would complain I for sure would know about it.
Repels oxidation and corrosion not atracts. One of my repairs was the pots in my wireless mouse which uses conductive plastic pots, its been 2 and a half years now, still working great.
I find it odd you say this will lead to problems:confused:
Anyway if reddish can show us a pick, we can maybe help him get a new pot which is a better solution all round. |
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| reddish75 |
ok, ive used silver paint, and my meter says its conducing, but i feel this won't last long? anyway heres a picture just in case anyone can help?
thanks |
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| EchoWars |
homemodder...WD-40 (or the carrier in the stuff, whatever it is) can attack and destroy some types of carbon tracks in some potentiometers. You don't guarantee a pot failure by using it, but you roll the dice each time you do.
It's all about the using proper tool for the job. You don't use boltcutters to remove the lugnuts on your car wheels because there are better tools to get the job done, and you don't use WD-40 on audio potentiometers for the same reason.
reddish75, put a couple of coats of paint on it. Each coat should be thin, and just wide enough to cover the break. There might be a problem with longevity if the painted section is at the low end of the travel where it gets the wiper across it a lot, but if the break is at the higher end, it won't see much duty and could last a very long time. |
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| jaycee |
Depending on the circuit, you can probably stick a regular potentiometer in there and ignore the balance control.
Looking at the pinout you would have to get a 2-gang potentiometer and install it with wires. My guess is this potentiometer has a common ground, hence 4 pins.
Really, you'd need the schematic to be 100% sure. |
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| jaycee |
Have now read the A400X service manual. This is a 2 gang pot with a "loudness" tap which is what R731/732 are doing. The volume pot is shown as VR701.
An ordinary 47K/50K log pot should work just fine. Simply ignore the loudness tap. You will probably need to fit it with wires, but provided there is a place behind the front panel to attach it by bolt, it should be fine. |
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| sakis |
I dont have .....but i do have some coaxial pots ( brand new ) that include both stereo volume and balance control and some models include also loudnes control .....
The thing is that i f i give you any of these ( i also have various range from 22K to 100K ) you will have to fit it out of the pcb with cables or a small mod .
I can also give this for free of course
regards sakis |
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| Mooly |
Many so called dedicated "electronic switch cleaners" as supplied by the electronics service industry were responsible for huge damage to cabinet parts due to attacking plastics over months and years. Have seen 100's of TV cabinets and remotes have to be binned through this. Never had problems with WD40.
On to pots and you can sometimes open them up and retension and move the wiper. Usually done this on cheap stuff, if it's a riveted design like an ALPS you wont be able to do this.
Get the proper pot from Pioneer :) |
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| reddish75 |
succes left channel now singing as it should, that silver paint worked a treat, now only right channel to get working, sounds as though its under water any ideas?
thanks for the offer sakis
thanks |
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| destroyer X |
I have used into vintage amplifiers my whole life... cleaning pots and avoiding noises...have never replaced... also switches were fixed, cleaned and lubricated too using the solution... considered one of the marvells of the last century.... used into weapons..bicicle chains... lockers... to protect aluminium panels, to keep watter distant from the automobile electrical parts, to automobile doors to avoid noise, to lubricate them...brake cables, well... thousands of uses as deeply penetrating lubricant..thin oil that uses to remove dust, oxide... interesting that can destroy potentiometers too.
Well..... since the eigthies i have not used anymore.... the amplifiers used no more conventional, traditional, standard potentiometers...they were using digital volume controls pushing buttons...no more WD40 on them.... i have used into the old Alps potentiometers..bigger than the ones used now a days... some of them had nice mechanical steps and centering grooves....nice those folks.
I see into those press contacts, the metal bubble covered with scotch adhesive tape used to loose glue because of WD40... could not use there because diluted the glue...but now a days we have better micro pressure switches that accepts oil alike WD40 without problems.
Interesting you say WD40 destroy potentiometers.... they used to fix in the past....maybe new potentiometers are more sensitive to destruction because of anti rust and thin oil solutions.... maybe manufactured with other kind of material..maybe now a days only a track of carbon is used over thin plastic flexible sheet.... old days you had solid ring of carbon.
WD40 used to solve problems, not to create problems... interesting modern days ideas and modern folks experiences.
I do not feel envy about you young guys (less than 35 years old).... your new world is worse... things are weaker.
regards,
Carlos |
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| jkeny |
I just started a thread on the very same topic http://www.diyaudio.com/forums/show...534#post1613534 & then found this thread - oops.
Anyway, I'm in the same boat except mine is physically broken & conductive paint won't fix it.
So I need a replacement - I'm mainly trying to find a physical fit for the Pioneer knobs & not too worried about the connections to PCB - even the resistance is not too critical or the 4 pin connection - 3 will do. Doesn't have to be high quality.
Mine is exactly the same as in the pic - so points to note are the dual D shafts (inner & outer) & lug or tag on the casing that you can see at the bottom right of the pic) which fits into a hole in the front panel.
Edit: Reddish, did you get both channels fixed? One interesting thing I found out when I took the pot apart is that the 4th pin allows you to connect another carbon track on the pot if one is faulty. If you need more info let me know Reddish.
Sakis, would any of your pots fit? |
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| jkeny |
Reddish,
I see some ID markings on my pot but most are illegible - can you make out what's on yours?
They are ALPS pots & ID starts 02 & ends 063-A |
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| reddish75 |
Hi, i have found whats wrong with my amp. The emitter resistor on the faulty channel has a crack in it, does anyone know where to source one from? (its the 0.33r 3 legged type)
I found a spares shop that sell the volume pots, however they are £30.00 each! but i think you can just add a normal pot and will work the same, except the balance. |
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| homertooties |
Hi should find resistors on ebay cheap
basically a 3 legged resistor is 2 in series with both middle legs linked,
way around it is to get 2 resistors of correct value ,which is important as they set the current for the output stage,twist 1 resistors leg couple of times around other solder it cut off excess and keep the middle leg you just created as long as other 2 outer ones and voila you have an equivalent part ,reason is 2 legs dont normally fit in same hole.....or if you are confident enough drill another 1 mm hole near other centre one in pcb and ,scrape laquer around hole underneath tin up ready for parts to be fitted...
Also you may find the 2 resistors will be too wide to fit in board with other parts,you can bend the legs so the resistors will stand at about
70 degrees making an m shape,you must make sure these resistors
stand about 6mm above board when soldered to aid with heat dissipation....hope this helps good luck |
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| jkeny |
Good work Reddish,
I fully agree with the advice from Homertooties, why pay over the odds for what is a simple part easily made up.
Also £30 for the pot is daylight robbery (does the guy in the shop have a mask & gun) - a shop that preys on the gullible unthinking consumer obviously - as I said in another post somewhere these are $5 pots at the very most. I hate these rip-offs. We, in these islands accept too readily this sort of mugging and don't protest enough. You should have laughed in the guys face for asking this price & maybe he would get sensible & eventually Pioneer would also </rant over>
<not over yet> When I tried to remove a piece of equipment from my local recycling centre they tried to stop me (but failed). I just find that the system is geared towards making sure we pay for everything. We pay €15 at the gate to bring in recycling. I found out that the computers from the recycling centers here are sold to a shop who dismantle them & sell parts back to the public. <now I'm finished> |
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| homertooties |
I forgot to add make sure you use ceramic or metal oxide resistors
not carbon normally 3 watts should do job...... |
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