Looking for a Data Sheet for old TI stero signal chip SN76105N.

Hello Russell, 

  We do have some older datasheets archived, and I have reached out to those who have access to see if they have any info on this device.  It may take several days to find out.  In the meantime, you could do a web search; I found some schematic references, and an interesting page at audioasylum that lists many compatible devices and gives some details. 

Regards, 

~Leonard   

 

I really appreciate your looking into this.
I'll have a look at 'audioasylum'.
I've had some help with compatable parts from contributors on 'AudioKarma'. They helped me get to 'Karlheinz Fischer' where I found pin info for the SN76105. I had found a data sheet for compatable part 'ECG720' which provided pin and feature info. Some of the compatable chips that come up do not have all of the features of the Hitachi part. All indications are that the Hitachi part and the TI part are feature and pin compatable. Can't find a data sheet for the Hitachi part either, but do have the service manual for the radio so the that schematic helps a bunch.
The next step is to see what Mouser can help me with. Mouser may be able to come up with a compatable part. I'd feel a little better about purchasing a part from Mouser than from an ebay seller.

Very well. It would be pretty fortunate to find something internally that is not already available from some source on the web.

Say - I noticed that your reply was for the SN76015N instead of the SN76105N. I trust that it is just transposed in the reply and that the search was really for the SN76105N.

Thanks again.

Hi Russell, Leonard is on vacation so I will reply.
I also looked for this SN76105 with Leonard, so I am sure he just transposed it wrong.
And I also found ECG720 with a list of comparables, all of which were very obsolete and information un-obtainium.

TI's obsolete device distributor, Rochester Electronics, has none of any of these parts.
So you may have to shoe horn in a deadbug fix with another amp, if you can figure out the specs.

I see many DIY circuits for FM Stereo Decoder on the web.

And what kind of receiver are you rebuilding?

This Ham is curious. KG5SUZ

73s to you. I have not renewed my license and was never very active on the 2 meter.

My neighbor is constantly going to sales and coming back with receivers from the 70's. He says he has place near down town dallas that specializes in selling the old receiver equipment. He has not offered any more info as to whether he is resaleing his radios and making money at it. I'm facinated by the stuff he comes home with so he has been showing it to me. It is the old high end Kenwood and the like, even turn-tables and speakers. Many would consider the stuff "boat anchor" but at one time it was top of the line.

He is not knowledgeable about electronics or repair but kleans up the switches with some contact cleaner and replaces bulbs. When he found out that I had a solder iron and some service experience we became "best buds".

This unit is a quad channel Fisher from '72 I think. I would guess that by looking at the amp transistors that it is around 30-40 watts. The AM works as expected and can blast you out. The FM audio level is low and the stereo indicator light does not come on. Sure appears this FM decoder chip has a problem. The chip should have some gain, but a scope does not show much if any, and the stero indicator pin from the chip appears to be floating.

It has the old phenolic boards which are not very tolerant of overheating the traces. I had a few pads come loose, but not separate from the trace, while I was recaping it. I had to drop to a lower wattage iron after I saw a couple the pads lift. Maybe if I continue helping him I'll be able to justify purchasing one of the temp controlled irons. He is retired and I am a couple years from jumping off of the payroll so maybe he will fund my hobby.

Thanks for expressing your interest. Do you have any experience with servicing equipment like this?

73s 2U2 Russell,
I work 10M officially, 11M also, 25-30MHZ, 60W, 1/2Wave 10M dipole.
Had my General about a year now.

Is this the Fischer 304 or 404 receiver?

First thing that comes to mind are the switch contacts.
I assume you must turn a knob from AM to FM etc.
That is the first place I would look.
I would think it has a large ganged rotary switch array with multiple contacts.

Why would the FM decoder go bad?
Seems unlikely.

Does the knob select FM and FM stereo, separately?
Is the sound low on mono FM?

If there are 'line out' signals, are their levels different in AM and FM modes.?