Good news!  It was the op-amp Hitachi FA-6007T  that died. I'm not sure if there are any other Hitachi radios using this early bird?

FYI a quick and dirty test of the audio section is to simply touch pin 1 and the radio should hum.

 

7 hours ago, 240260280 said:

I thought this was yours: https://www.gtr.co.uk/forum/236658-1969-nissan-s20-twin-cam-engine-rebuild.html ?

Yes but what's the connection with zclub.net?

From here:

8 hours ago, 240260280 said:

btw your UK website is great. It often comes up in searches...

They are two - completely unconnected - clubs and forums.

My error. Excellent sites and content none the less.  Alan your genius comes to light on the GTR site!  Nice stuff!

Just ordered an opamp to repair the radio. All is good.

Old (Pin 1 is on left side above. There is a raised line on the left edge)

New

Edited July 17, 20195 yr by 240260280

15 hours ago, 240260280 said:

Pin 1 is on right left side

Uhhhh.... That might make sense to someone, but I'm not one of them. 

Out of curiosity, do you have a datasheet for that part?

Sorry. I corrected entry but left the wrong right in. <<< makes sense right? Fixed now.

 

Sorry. No I do not have data sheet. I would love to see it too  I think the IC is more than just an op-amp as it feeds back to the auto tuning circuit. See Pin 7's output below.

I will guess that the op-amp function can be substituted with a compatible op-amp but you will loose the auto tuning without developing the associated circuitry to trigger an amplitude lock on a signal or maybe it is a mute while tuning control?

13 minutes ago, 240260280 said:

 the wrong right in. <<< makes sense right?

Yup! I Got it!  Haha!!

So not that it really matters, but that's an AF (Audio Frequency) amp, not an op-amp.

Good luck with the repairs. I paid my way through a couple years of college fixing audio-visual equipment. One of the things I learned is that 95% of all failures are blown output stages. Even if the problem does not appear to be a blown output, it might be anyway. 

I bravely swapped bad unit's output stage to working unit and it continued working.  I put working units output stage in bad radio an no change. 

 

I then moved good AF SIP to bad radio and it worked... risky but easy.   I did verify all voltages in power transistors were the same before swapping so low risk in the end.

@Captain Obvious  attached below is schematic with details of FA6004 audo amp in 1972 portable Hitachi radio. Same 8pin SIP module. It may be similar in some ways. The best I can do.

FA6004 Details.pdf

Cool. Neat find. based on the pin numbers and similar use in the schematics, I would concur that there are a lot of similarities.

Good luck with the repair. Sounds like you're almost done!