Hitachi TM-1081-ZB Radio Repair Thread

[240260280]

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.

 

[HS30-H]

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.

[240260280]

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

[240260280]

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, 2019 by 240260280

[Captain Obvious]

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?

[240260280]

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?

[Captain Obvious]

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. 

[240260280]

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.

[240260280]

@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

[Captain Obvious]

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!