Akai GX-230D no input

[barrywebb]

Hi all ive got hold of a vey nice Akai gx230d cleaned and re Greased with lithium grease plays well but on record you have to turn the levels up and the tape play back is much lower than the source.
Today i replaced all the 2sc458 transistors on both boards one board i used new 2sc458 and the other on i used 2sc2240 transistors but on both boards i only replaced the old 2sc458 transistors all had black legs..
Anyway all done but now i have no input at all left or right tested after one board and it was the same.
Playback works fine i think i have missed something but not sure what cant see anything out of place anyone have any ideas?
Its driving me mad lol.
Barry.

[barrywebb]

Today i have removed the source switch from the machine and stripped it down and cleaned all the surfaces its all nice and shiny inside now anyway all put back together and still no input.
I also removed all the 2sc458 transistors i fitted yesterday and replaced them with 2sc2240 transitors i was told they are a better option so thats 16 fitted in total there are 8 2sc945 transistors left on the two boards 4 on each but im told they should be fine anyway the machine was working ok untill i fitted the transistors ive double checked all my solder joints and all is good just dont understand why it will not and yes there is also power going to the board.
Please help me im going MAD...

[NorfolkDaveUK]

I doubt its anything to do with transistors , I would Imagine the record head is out of alinment and / or it needs calibrating is all .

[ms660]

Circuit knowledge, a multi meter and a scope will pin most faults down PDQ....Anyone use this ancient method...

Lawrence.

[Station X]

There's still a few of us left!

[TonyDuell]

Originally Posted by ms660

Circuit knowledge, a multi meter and a scope will pin most faults down PDQ....Anyone use this ancient method...

Lawrence.

Do not get me started!

I generally explain that fault finding involves knowing (in detail) what the device should be doing (including voltages, waveforms, etc). That, in the case of the things I work on, involves the circuit diagrams, microcode source listings and the like.

Then finding out what the device actually is doing. Since you can't directly sense the signals, this involves the use of the multimeter, 'scope, logic analyser, etc.

Then you work out how the actual behaviour differs from the expected behaviour and thinking what could have failed to cause it. Of course you do more tests and measurements to home in on the problem

Then, and only then, do you replace any parts.

This method works for me (and even if I say so myself, on things a lot more complicated than the typical units discussed here).

[arjoll]

Originally Posted by ms660

Circuit knowledge, a multi meter and a scope will pin most faults down PDQ....

With an Akai of this age, some contact cleaner and working all the switches will also fix most problems

[ms660]

And if it doesn't...hey man...mass recap, mass TR change and if it all goes tits up ask on here....hey ho....seen it all before.

Lawrence.

[Radio Wrangler]

Did you keep all the parts you took out? You may want to put them back.

How confident are you that the new 2SC458 and then the new 2SC2240 were not fakes? Were they tested before fitting? The problem is real, there are many, many parts floating around that turn out to be something else marked up as a more valuable part. The risk doesn't guarantee that this is where your problem lies, but it's a possibility. Other possibilities are bad solder joints, solder splashes, broken PCB tracks, broken wires... It takes plenty of care and experience to get the risk of introducing problems right down, and the people with this level of experience tend to test things and replace only the necessary parts once they've isolated the location of a fault,AND determined what the root cause was.

Shotgun replacement techniques have their place, but they have a bad track record if used blindly as a substitute for understanding.

I do a LOT of troubleshooting, often on prototype equipment, so I don't even get the luxury of knowing that anything else to the design has ever worked before.

David

[barrywebb]

Ok update seems the schematic that i got for the record amp board was incorrect that is i had to print it off on a4 and the turn it over hold it up to the light and then it was the correct way for the board.
I had fitted the transistor in the wrong way i followed to schematic first time them looking at the board and the schematic the schematic was upside down.
All done now put back together and working.
thanks for all your help.
Barry