amp been in for repair, not fixed need advice to trace faults

[anatech]

Hi mrlennon,
If these are normal resistors with leads, you can use 1/4W. For SMT types, there are others that will fit. You need the same or higher wattage.

Send these folks an email, or stop by a shop while you are in the area to pick them up. These are very common parts, most repair shops should have them on hand.

-Chris

 

[mrlennon]

ok thanks i have emailed them will let you know what they say,



the origanals are

Min Resistor carbon 75 OHM 1/5W J
&
Min Resistor carbon 22K OHM 1/5W J

would a Min Resistor 75k Metal Film 0.6W work as a replacment for Min Resistor 75 OHM 1/5W?

and a

22K metal film 0.6w work as a replacment for Min Resistor 22K OHM 1/5W ?

as i see maplins sell resistors here: http://www.maplin.co.uk/Search.aspx...owPics=true&Stock=28&MinPrice=0&MaxPrice=9999

also i think it would be wize to repair 1 channel at a time dont you think?

thanks.

 

[Stones]

ok thanks i have emailed them will let you know what they say,



the origanals are

Min Resistor carbon 75 OHM 1/5W J
&
Min Resistor carbon 22K OHM 1/5W J

would a Min Resistor 75k Metal Film 0.6W work as a replacment for Min Resistor 75 OHM 1/5W?

and a

22K metal film 0.6w work as a replacment for Min Resistor 22K OHM 1/5W ?

as i see maplins sell resistors here: http://www.maplin.co.uk/Search.aspx...owPics=true&Stock=28&MinPrice=0&MaxPrice=9999

also i think it would be wize to repair 1 channel at a time dont you think?

thanks.

mrlennon,

Your replacement selection is metal film and the original are carbon film although this will make no functional difference it could affect the sound depending on use (location).

1/5w = 0.2watt so assuming that the originals are actually this wattage value and not 1w or 5w anything over this wattage value will be fine assuming it physically fits or can be made to fit.

It would be a good idea if you posted a picture of these resistors so that the members can ensure that they are not anything unusual, Example flame proof.

There is probably another reason for the resistors failing.

Good luck.

 

[anatech]

Hi mrlennon,
The short answer is that , yes, they will work. You can stand them up if they are too long to fit laying down. Some metal film resistors are inductive, that you can not tell without more advanced equipment. So give them a try.
Put a light bulb in series with the AC power in case there are more problems. If the bias is high, or suddenly goes high, and cannot be lowered enough, the unit may be oscillating. If you have an oscilloscope you can see this on the output.

-Chris

 

[mrlennon]

heres a picture of the resistor.

 

[anatech]

Go for it!

-Chris

 

[hjelm]

Was it 75 ohm or 75k ohm, there seems to be a difference in you r mail, typo?

 

[anatech]

Good point hjelm,

mrlennon, the value has to match. The wattage can be increased a little.

-Chris

 

[mrlennon]

in the service manual it says 75 OHM 1/5W,

 

[anatech]

And that's what I see in your picture. Replace and report once you have things running.

-Chris

 

[mrlennon]

so i gather the Min Resistor 75k Metal Film 0.6W will work ok, as a replacment for the origanal Min Resistor 75 OHM 1/5W?

and the 22K metal film 0.6w work as a replacment for the origanal Min Resistor 22K OHM 1/5W ?

i have just ordered some of the parts so hopefully should be here in next few days the rest are currently out of stock should be here in 7-10 days, so what i might do is as 3 channels need repairing is take the parts out of the one of the other none working channel if they test ok for now see how i get on untill rest of parts arrive.

 

[anatech]

Hi mrlennon,
No. You need to replace the 75 ohm unit with a 75 ohm unit. 75K ohm will appear to be an open circuit, the resistance is 1000 X (=K) higher.
-Chris

 

[mrlennon]

ok so i will need to get the proper resistors i take it,?

any ideas where i could get them?

thanks

 

[anatech]

Hi mrlennon,
If you were in Canada, no problem. You are in the UK so I don't know.

A repair shop should have them on hand. There must be other companies that supply spares.

DIY members from the UK, help this poor guy out please.

-Chris

 

[johnnyx]

Hi mrlennon
Here in the uk Maplin sell the components you require. They have branches in many towns and cities, probably one near you. They don't sell as many components as they used to, but they're sure to have the resistors. They do mail order too. There are other places, eg CPC , but they're mail order only. Both companies are big and both give good service.
Hope this helps.

 

[mrlennon]

well i had a quick look on http://www.maplin.co.uk/ and farnell.

for

Min Resistor 75 OHM 1/5W
&
Min Resistor 22K OHM 1/5W

cant seem to find the ones i require unless i somehow missed them? anyone have any more luck finding them?

 

[johnnyx]

It looks as though they sell far fewer components than I thought. Maybe they will stop selling components altogether, if there's more profit in gadgets and computer add - ons.
You can use two 150ohm resistors in parallel, that will equal 75ohms, something like these would do.

Edit;- maybe the absence of some values on the website is a fault of the site, call them to check.

 

[mrlennon]

so if i do buy 2 of these resistors and put them in parallel, will these defenetly work and be ok for a substitute Min carbon Resistor 75 OHM 1/5W?

i would like to buy the proper resistor however finding it hard to track one down, but if useing them 2 resistors will work i wil give it a shot however want to make sure they will be ok first? also concidering they are metal film resistors not carbon.

 

[Stones]

RE:well i had a quick look on http://www.maplin.co.uk/ and farnell.

for

Min Resistor 75 OHM 1/5W
&
Min Resistor 22K OHM 1/5W

cant seem to find the ones i require unless i somehow missed them? anyone have any more luck finding them?


More luck follows

RESISTOR, 0.5W 5% 75R Carbon Film Order Code: 771818

RESISTOR, 0.5W 5% 22K Carbon Film Order Code: 509991

farnell

 

[anatech]

Well mrlennon

There you go, mark stones have found them for you.

Generally you will find 1/4W and 1/2W as they are common values. 1/5W are not found anywhere but by special order. I think someone setting up the BOM (Bill of Materials) was being silly.

-Chris