Sharp Vz 2500 No audio from cassette either playback or record

[Brother_Kornhoer]

Greetings, currently working on my Brother's vz 2500. He recently purchased off the original owner. We had to change all the belts as to be expected as all were goop. All functions now work perfectly (albeit requiring new stylus) however the tape cassette neither plays audio or records audio. Mechanically all appears fine. Using a tested recording on a tape, nothing plays at all. Trying to record from fm or other inputs produces a blank tape. Where would one begin to look please? Equipment wise, I have access to a solder station and a multimeter plus hand tools.
Please advise

 

[floyd]

I have this boombox and most of the time I have to mess with the function buttons to get clean sound output on anything.

 

[docs]

If youve had the deck out have you ensured connectors are in place correctly? Continuity test from heads to end of cables to confirm cable integrity.

 

[Brother_Kornhoer]

Cheers for the quick replies!
Docs, continuity test shows making good connection between deck and preamp PCB.

Jvc Floyd,the selection buttons have been cleaned with pcb cleaner, when pressing the buttons, you can hear the speakers cut out/ swap channel. I have tried manipulating the button to see if anything changes but no luck. I can also tell the preamp is getting voltage as get speaker noise when tapping pins on it. Have tried tweaking the PB pot to no avail. Also, you cannot record to tape. It's almost as if the tape section isnt being routed to any sort if audio signal in or out. Could that be a broken head?

 

[docs]

Looking at the block diagram, the first thing to check is the record bar itself, did you clean this thoroughly?
Check if you get anything at pin 7 of IC203 the Dolby chip, there are muting transistors before it Q201 and Q202 which sounds the possible cause.
Before these you need to ensure that IC201 the palyback AMP is good.



Check voltages at this IC then move towards the Dolby IC.
In pins 6 and 8, out pins 2 and 12.

 

[Brother_Kornhoer]

Thank you again Docs, very informative. I am a little concerned, pin 6 and 8 I get 0.58 v, pin 2 reads 0.8v and 0.98 v on pin 12. These are super low

 

[docs]

It looks like pin 1 is vcc, what is the voltage at pin 1?

 

[Fatdog]

This might be a long shot, but while you have it apart, spray a little bit of some DeOxit into the record bar mechanism and work it manually. If you don't know what the record bar is, here's a thread:

Record Switch Bar Example

A few boombox problems are caused by a dirty, or faulty, record switch / bar. Most of the times, the primary symptom is a high-pitched squeal when playing cassettes. Thorough cleaning with DeOxit or some other electronics cleaner will generally be the simple fix. Here is an example of what a...

boomboxery.com

 

[Brother_Kornhoer]

It looks like pin 1 is vcc, what is the voltage at pin 1?

0.008v on pin 1. Dexit spray or the syringe variant? Contact cleaner is a little vague in England. I used the wd40 one to clean the volume slider

 

[docs]

If in UK go to CPC and order contact cleaner.

It looks like that voltage at pin 1 is waaaay too low. Are you testing while deck is playing?

Take a look at the C211 cap and R207 1/4W resistor voltage values here, just try and determine where your voltage drops from 9v. You may need to desolder pin 1 to get an accurate check. With pin 1 disconnected, if 9v at IC side of r207, I would assume the IC is faulty.