Realistic STA-7 receiver

anatech

Administrator
Paid Member
2004-06-06 8:31 pm
Georgetown, On
Hi rpapps,
Interesting problem. Was the chip an exact replacement? I mean the exact same part number - no subs or replacement brand. What was the chip number?

It sounds like the on board muting is not happening if this chip has it. A leaky cap used as a DC block may cause this also.

-Chris
 

Netlist

diyAudio Moderator Emeritus
2003-01-18 9:50 am
This info comes from an paper lying around here, I have no experience with the amplifier. It also says to check for a short or nearly short between pin 1 & 3 of the output IC's. It's not a big deal to change four diodes, one never knows. :)

/Hugo
 
STA-7

Hi Chris & Hugo
The replacement chip is a genuine Hitachi HA-1370.
There is a swith-on muting circuit but it is common to both channels.

I have replaced the power supply diodes and checked all capacitors with an ESR meter. Even after >20 years, they still read good as new. (I hate to throw anything away)

I've gone over the board with a magnifing glass looking for dry joints or cracked tracks.
I guess the next step is to order another replacement chip.
Thanks for all your input.
Cheers
Rob
 

anatech

Administrator
Paid Member
2004-06-06 8:31 pm
Georgetown, On
Hi Rob,
Just for chuckes and grins, pull the 1uF input coupling caps out and try it. They may still be leaky. I use a $6500.00 HP LCR meter to check caps, I don't trust anything less anymore. Your ESR meter may not catch leakage in high impedance circuits.

Besides, caps are cheaper than chips.

-Chris