Author Topic: Rotel service  (Read 304 times)

Offline PJFourie

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Rotel service
« on: December 07, 2017, 07:32:15 AM »
Hi guys. Hope you are all well. I have a rotel ra-820a and i would like to have it serviced by someone who knows what theyíre doing, unlike the guys at Xbytes in edenvale who soldered wires on top of the fuses


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« Last Edit: December 07, 2017, 07:47:51 AM by PJFourie »

Offline PJFourie

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Re: Rotel service
« Reply #1 on: December 07, 2017, 07:46:58 AM »
Iím in Modderfontein area.


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Offline prajayn

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Re: Rotel service
« Reply #2 on: December 07, 2017, 09:06:45 AM »
Nilam. But hes in Randburg. (011) 789-8578‬

Offline thenoizeguy

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Re: Rotel service
« Reply #3 on: December 07, 2017, 09:38:01 AM »
+1 Nilam, but unless there's something wrong with it, leave it as is.
Expensive cables come in fancy silk lined wooden boxes to make you feel better about spending a fortune on them.

Offline El Sid

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Re: Rotel service
« Reply #4 on: December 07, 2017, 09:52:58 AM »
+1 Nilam, but unless there's something wrong with it, leave it as is.

Well if someone  from Xbytes in edenvale soldered wires on top of the fuses, there's almost certainly something wrong!  ;D

Offline pwatts

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Re: Rotel service
« Reply #5 on: December 07, 2017, 11:43:01 AM »
As per an earlier heated thread, Xbytes probably just tried to improve the sound quality by bypassing fuses..

Offline Rotelman

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Re: Rotel service
« Reply #6 on: December 07, 2017, 02:41:45 PM »
Those 820s are really basic units and you should not be afraid to open her up and do some checks yourself.

If I were you, I'd open her up, undo the soldering your service provider did, change the fuses give it a good clean out and measure the bias values and compare to the manual.

None of this is really difficult to do. If your bias values do not look OK, be careful with adjusting these. If they are OK (same or within 90% of the published values) and your unit is clean with new fuses, the only other thing that can trip you up is some dirty volume and selector pots. Lots of good info out there to clean these too.

good luck

Offline PJFourie

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Re: Rotel service
« Reply #7 on: December 07, 2017, 08:04:25 PM »
Sure, but a fuse is a protection device so itís there for a reason.


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Offline PJFourie

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Re: Rotel service
« Reply #8 on: December 07, 2017, 08:09:05 PM »
Thank you Rotelman. I will open it up myself. I bought new fuses and some contact cleaner today. Also downloaded a service manual so Iíll read up on the adjustments. Thank you.

How do i go about cleaning the inside of the unit?


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Offline JANNAS

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Re: Rotel service
« Reply #9 on: December 07, 2017, 08:49:42 PM »
When you adjust bias and DC offset make sure you know what you are doing. Have your meter on dc milli - volts and nowhere near amperage !! Know where to check over the emitter resistors and do not let the probe slip. You might have "lang krokodil trane " over x-mas instead of music. If not sure, ask someone knowledgeable to do it for you !! ;) 

Offline PJFourie

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Re: Rotel service
« Reply #10 on: December 07, 2017, 10:23:47 PM »
Thank you for the advice.


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Offline BoerieZA

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Re: Rotel service
« Reply #11 on: December 08, 2017, 10:27:13 AM »
Or.....OR....you could just let the Legend-Known-As-Nilam sort you out?

Offline Rotelman

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Re: Rotel service
« Reply #12 on: December 08, 2017, 10:49:06 AM »
Thank you Rotelman. I will open it up myself. I bought new fuses and some contact cleaner today. Also downloaded a service manual so Iíll read up on the adjustments. Thank you.

How do i go about cleaning the inside of the unit?


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Cleaning-wise, it depends on how she looks inside. You might need to blow it out or vacuum it out at worst or you might get away with a gentle clean using a soft cloth. Earbuds work well for the hard-to reach places. Take precautions as some of the capacitors will still be charged. Don't open and clean immediately after using the unit. Make sure it's been off a day prior to opening it up. Make sure you don't use any conductive material in this process. Go gentle and slow on this step.

Bias-wise : I will again caution you on the actual adjustment side of things, as this could lead to damage of the unit and besides I doubt if you'd need to adjust in any event.

First check the values and compare to the design values.
The service manual (normally available on free download) will detail the steps, equipment and sequence required. You can check the schematic to find the TP1, TP2, TP3 and TP4 test points. On these models these points are normally bare steel pins sticking up about 10mm form the board. They should be numbered on the board, but double check on the schematic. The Service manual will stipulate the use of a DC milli-volt meter and detail which lead goes on which test point in each step and what reading you should get. (4mV in this case?? Check the manual) . Use a good quality multimeter for this. The el-cheapo's might not provide true readings at these low levels.

Follow the Manual's instructions on warming up the unit prior to testing. The unit will thus be on and open, so the obvious basic precautionary measures apply with live electrical open units.....Be careful where you put your fingers and your leads. Do your readings as the manual guides you and don't be stressed if your reading does not match 100%, as it probably won't. Use your discretion and consider adjustment if the two channels are obviously unbalanced and/or when the actual reading differs form what it should be by more than 10% or so. Rather be lower than higher. Should you want to make adjustments, the service manual will stipulate which variable resistor to adjust for which channel. Think this operation through before you start, as you'd want realtime readings whilst adjusting, which can be tricky if you're doing this alone and for the first time.

When you done, have a beer and should you find yourself thinking which other unit you'd like to open up and check, know that you're a tinker.....


Offline Neil

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Re: Rotel service
« Reply #13 on: December 08, 2017, 01:22:48 PM »
If it were me - take it to Nilam - he did a wonderful job on my NAD - looks like he even added a heatsink...
and its working better than it did before it went in
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