CR-2020 Repair Advice

sajjad amer

Active Member
When switched on it lighted up and there was no relay click. Signal meter needle was in the middle. So I did the service bulletins and changed voltage regulators to TIP41.

After service bulletins the lights are no longer working. However unit still powers on and meters are where they should be but no relay click. I have literally rebuild the whole board as it was burnt, re-flowed the solder and where needed applied jumper wires. I have recapped it and double checked to make sure black earth wire is soldered where it should be still no relay click and no lights which were working before I messed with it.

I have one confession though, during service upgrades I have gone for same value but higher wattage i.e 5 watts instead of 3 1/4. I have changed the 33 ohm and 2 fuse resistors, 22 and 10 ohm each to 5 watt.
could this be the reason for relay not clicking. ? Could some one please guide me what am I missing here ?
Many Thanks and Happy Easter.
 
I have one confession though, during service upgrades I have gone for same value but higher wattage i.e 5 watts instead of 3 1/4. I have changed the 33 ohm and 2 fuse resistors, 22 and 10 ohm each to 5 watt.
Not a wise decision. Please list the FRxxx #´s for the fusible resistors you replaced.
 
Last edited:
22Ω @ 150ma ------> no larger than 1/2 watt with flame resist coating
10Ω @ 220ma ------> no larger than 1/2 watt with flame resist coating
These are suppose to be fuses.

Would you replace a 2 amp fuse with a 20 amp fuse ?

Well thats close to what you did using a 5 watt resistor ...
 
Last edited:
but no relay click.
Need to check for DC voltage at the output of each power amp. Check at a testing point before the protect relay contacts. You may have a shorted output transistor or and issue in one of the power amplifier assemblies. And the protect circuit/relay is working like it should.;)
 
Last edited:
Page 12 of the service manual shows a illustration of one amplifier assembly. Note the solder lugs marked O and E along the top of the circuit board. Put your meters black test lead on the lug marked E (ground) and your red test lead on the lug marked O (output). Check for DC volts with power applied. This is also your test point for DC offset. It should only be an few millivolts. Ideally zero volts.
 
Last edited:
Be extremely careful. Don't short Test point O to test point E with power applied. Or you will definitely destroy and output transistor or two. If there not already shorted.
 
Last edited:
http://cpc.farnell.com/webapp/wcs/s...estType=Base&partNumber=RE07469&storeId=10180
http://cpc.farnell.com/webapp/wcs/s...estType=Base&partNumber=RE07467&storeId=10180
http://cpc.farnell.com/webapp/wcs/s...estType=Base&partNumber=RE07462&storeId=10180
Not a wise decision. Please list the FRxxx #´s for the fusible resistors you replaced.
Apologies for late reply, had to work over holidays as replacement. Above are the links to the resisters I used, there was no Fusible option, so I used ordinary resistors I will search for correct parts and rectify this issue.Thank you for advice.
 
Page 12 of the service manual shows a illustration of one amplifier assembly. Note the solder lugs marked O and E along the top of the circuit board. Put your meters black test lead on the lug marked E (ground) and your red test lead on the lug marked O (output). Check for DC volts with power applied. This is also your test point for DC offset. It should only be an few millivolts. Ideally zero volts.
Right Side is -4mv
Left Side is -3mv
Kindly guide me about next step, many thanks in advance.
 
Right Side is -4mv
Left Side is -3mv
Kindly guide me about next step, many thanks in advance.
Nothing wrong with the amplifiers..That leaves us with either the protect circuit itself or the power supply for the protect circuit.
 
Need to measure the DC voltages around TR702 on the power supply board in the protect circuit.
B. -- ?
C -- ?
E -- ?
 
Last edited:
Have you replaced any capacitors in the power supply yet ?
 
Reinstalled the transistor. I have only recapped the vertical board not the horizontal board as yet. Would you suggest I do that? I wanted to fix it first before starting complete recap, but happy to do as per your expert advice.
 
@avionic - did you see the service bulletins re. fusible changes ?

My first thought was to completely agree with your fusibles comments - but, there are a couple of service bulletins on the hifiengine site specifically making the changes (more or less) as Sajjad's made.
 
Back
Top Bottom