Search found 14 matches

by bambadoo
Sat Jan 16, 2021 5:12 pm
Forum: Amplifiers
Topic: MF-2500a - Service Manual
Replies: 5
Views: 1099

Re: MF-2500a - Service Manual

Thats me that did the repair on the amp. It became perfect.
Schematic is provided here
https://www.conradjohnsonowners.com/vie ... f=17&t=128
by bambadoo
Wed Mar 14, 2018 3:07 pm
Forum: Amplifiers
Topic: MF2500 throwing 68 DCvolt out on right channel
Replies: 21
Views: 4116

Re: MF2500 throwing 68 DCvolt out on right channel

It plays extremely well. Had a ground loop problem with one of my preamps. That was fixed and now it is dead silent and absolutely no transformer humming also. According to my knowledge the only "soundwise" difference between a 2500 and a 2500A is the new discrete rectifier diodes. jahatl5...
by bambadoo
Mon Mar 12, 2018 2:29 pm
Forum: Amplifiers
Topic: MF2500 throwing 68 DCvolt out on right channel
Replies: 21
Views: 4116

Re: MF2500 throwing 68 DCvolt out on right channel

Yes - unplugged for about a year :)

Now it sings..

Schematic coming soon to an email near you..
by bambadoo
Mon Mar 12, 2018 5:20 am
Forum: Amplifiers
Topic: MF2500 throwing 68 DCvolt out on right channel
Replies: 21
Views: 4116

Re: MF2500 throwing 68 DCvolt out on right channel

Thanks alot for your reply :) Started up my "fixed" MF2500 yesterday. No smoke, no hum in transformer. Adjusted dc offset and bias. Looks stable and fine. Will do some more testing perhaps today. Also have done some small modifications. And as far as I understand - it seems as the biggest ...
by bambadoo
Thu Mar 08, 2018 2:58 pm
Forum: Amplifiers
Topic: MF2500 throwing 68 DCvolt out on right channel
Replies: 21
Views: 4116

Re: MF2500 throwing 68 DCvolt out on right channel

Thanks alot for a good answer.
Did they respond on why it threw 68Vdc on right channel?
by bambadoo
Sun Mar 04, 2018 4:11 pm
Forum: Amplifiers
Topic: MF2500 throwing 68 DCvolt out on right channel
Replies: 21
Views: 4116

Re: MF2500 throwing 68 DCvolt out on right channel

Did CJ say what was wrong with the amp? What was fixed?
by bambadoo
Fri Feb 23, 2018 4:22 am
Forum: Amplifiers
Topic: MF2500- Thoughts on those who've had it; what to expect good and bad
Replies: 2
Views: 746

Re: MF2500- Thoughts on those who've had it; what to expect good and bad

Have one. Been on "service" at my home for 1 year. It is finished. Havent powered it up yet :)
by bambadoo
Wed Jan 03, 2018 4:53 am
Forum: Amplifiers
Topic: MF2500 throwing 68 DCvolt out on right channel
Replies: 21
Views: 4116

Re: MF2500 throwing 68 DCvolt out on right channel

Have one that did excactly the same. Many parts are fried including one pair of output transistors. Look here http://www.conradjohnsonowners.com/viewtopic.php?f=17&t=1118 and here http://www.diyaudio.com/forums/solid-state/306733-conrad-johnsen-mf2500.html CJ was kind enough providing schematics.
by bambadoo
Mon May 01, 2017 3:08 am
Forum: Troubleshooting/problems/manuals/schematics
Topic: CJ MF2500 fault - smoke
Replies: 6
Views: 2026

Re: CJ MF2500 fault - smoke

Q13 (small signal) mje340 on the left channel was also gone. CJ has stopped responding. Anyone know where to get a service manual? After it is finished I will chech bias dc offset and so on. Also did a recap of the psu and changed one fuseholder there. http://www.hifisentralen.no/forumet/attachments...
by bambadoo
Sat Apr 22, 2017 7:55 am
Forum: Troubleshooting/problems/manuals/schematics
Topic: CJ MF2500 fault - smoke
Replies: 6
Views: 2026

Re: CJ MF2500 fault - smoke

Only one pair of output transistors were gone.
1 2sc3282 and 1 2sa1302..

Anyone know where to get a couple of genuine Toshibas?
by bambadoo
Fri Apr 21, 2017 6:25 am
Forum: Troubleshooting/problems/manuals/schematics
Topic: CJ MF2500 fault - smoke
Replies: 6
Views: 2026

Re: CJ MF2500 fault - smoke

A loose fuse holder (only soldered at one end to pcb) Q12 (mpsu60l), Q23(nsdu57) and R12 (100r) minimun are broken on left channel. Waiting for some equipment so I can du some more digging..
Probably more that is broken.
by bambadoo
Wed Apr 19, 2017 5:26 pm
Forum: Troubleshooting/problems/manuals/schematics
Topic: CJ MF2500 fault - smoke
Replies: 6
Views: 2026

CJ MF2500 fault - smoke

Hi, have had this for a while but have never tried it Anyway - replaced all fuses (3 were blown) just to test. On fuse on the back and 2 on the pcb. Connected a DMM on each loudspeaker terminal and fired up. Left channel showd 72Vdc - Right channel ~100mV. After some seconds a bit of smoke appeared ...
by bambadoo
Tue Apr 18, 2017 5:08 pm
Forum: Member Presentation Thread
Topic: New member from Norway
Replies: 1
Views: 752

New member from Norway

Hi there. Have alot of equipment including a MF2500.
It has some issues which I hope can be fixed.