RXD26L Kenwood hi-fi schematic / advice please

[zen]

Hi all , just embarking on my next project .

Shuts down into protect mode shortly after power up .

Audio output devices measure good ,plus no DC voltage at speaker terminals before protect kick in .

There is evidence of cap leakage on the power / audio board , which might be a good place to start .

[zen]

Re: RXD26L Kenwood hi-fi schematic / advice please

My money is on caps

After leaving unit for a while , then making several attempts , it finally powered , without protect kicking in .

[zen]

Re: RXD26L Kenwood hi-fi schematic / advice please

Checked through the board & replaced any suspect caps .

The two main culprits were C29 & C30 ( 100MF , 16V ) , which had leaked out .

They are red in colour & remind me of the same , or similar types that used to fail on Toshiba CRT sets , on the frame circuitry .

Now powering , but won't have bench space to test till tomorrow .

[stj]

Re: RXD26L Kenwood hi-fi schematic / advice please

red caps?
the only old red caps i know are Dubillier,

[redwire]

Re: RXD26L Kenwood hi-fi schematic / advice please

Never seen red "hi-fi" caps from Japan, maybe Rubycons? "A Class Amp" marked on the board so it might have had some.

You won't read anything at the loudspeaker terminals when the prot relay is not pulled in. You have to measure DC offset at the plate emitter resistors.

If the DC protect is false tripping, I'd replace the negative feedback caps they get damaged if there ever was a lot of DC (shorted O/P transistors).

Couldn't find the schematic but the amp section board looks cut'n'paste on other Kenwood gear.

[lti]

Re: RXD26L Kenwood hi-fi schematic / advice please

The red caps look like the Elna "long-life" caps that were used in some power supplies in the early 1990s. They were known to leak.

[budm]

Re: RXD26L Kenwood hi-fi schematic / advice please

What DC V do you get with ref to the circuit ground on the middle pin of the white power resistors of both channel AFTER the protection kicks in?

[zen]

Re: RXD26L Kenwood hi-fi schematic / advice please

Here you go guys ( see picture )

Main cause of issue ,the 2 red caps . Hi-fi now working on test .

85 degree types .

[zen]

Re: RXD26L Kenwood hi-fi schematic / advice please

Next issue with this thing is that CD player not functioning .

Disc will spin , but no TOC .

Replaced the reader KSS210A , but same issue remains .

[stj]

Re: RXD26L Kenwood hi-fi schematic / advice please

did you scope the eye pattern and adjust the laser?

[zen]

Re: RXD26L Kenwood hi-fi schematic / advice please

Just swapped laser as i had one in stock.

Can't really afford to spend more time on it till i speak to customer .

[zen]

Re: RXD26L Kenwood hi-fi schematic / advice please

If i had a surplus of hair ,would have pulled it out by now .

What an absolute pain in the ass .

First thing that threw me was the fact that the brand new laser i had fitted was faulty .

After i had finished swearing , continued with repair .

Turns out original laser was ok .

Issue with the turntable motor , which i swapped out from another deck .

Then started to play , but something was rubbing .

Initially i suspected turntable height not correct , but turned out to be spot on .

The CD mechanism sits on another plate & between these two are rubber dampers which had become brittle .This had caused CD mechanism to sit lower onto the plate , hence further away from turntable clamp , which was causing the rubbing .

Took me ages to find substitute rubber dampers that would work well .Pretty much exhausted my entire collection of scrap mechanisms .

[R_J]

Re: RXD26L Kenwood hi-fi schematic / advice please

Did you unsolder the protection shorting pad on the new laser?

[zens electronics]

Re: RXD26L Kenwood hi-fi schematic / advice please

Certainly did RJ

Sometimes supplier gets a bad batch of lasers

[zen]

Re: RXD26L Kenwood hi-fi schematic / advice please

Well , this is the repair that just keeps giving .

Next problem , CD play very sensitive to external vibrations .

To solve this issue i adjusted pot next to empty connector almost fully clockwise .