Sanyo M-1150 tape recorder (1979). - UK Vintage Radio Repair and Restoration Discussion Forum

Gel38guitar · 18th Dec 2022, 12:15 pm

Hey guys,
I recently bought a used tape recorder. (See title) All of the buttons and functions seem to work fine, however, upon inserting a tape all i hear from the speaker (and headphones jack) is static. Sometimes i can make out a voice, but it's very faint.

I saw a guy on Youtube using a heatgun to heat up the soldering points on the circuit board. It worked after this process. I noticed discoloration in the video on his circuit board. I have not done this as I find it very risky. Is there a better way to get the speaker/headphone ports working? And is it inded the soldering points that need warming up, or another issue maybe? (The speaker is in good condition).

Thanks for any help.

Uncle Bulgaria · 18th Dec 2022, 3:04 pm

Yes - there are numerous better ways of doing it. First, find what the problem is, which needs some deduction and logic. If the signal is being lost between the input and output, you need to narrow down where that is happening.

If the man in the video had success with a heat gun, it implies there was a poor solder joint which the heat gun melted and reformed. A better way is to inspect the circuit board with a magnifying glass to look for poor joints. This could be a visible crack, or a joint that looks dull and grey rather than shiny.

More likely is that the signal passes through a switch (usually play/record) which has got oxidised and dirty and isn't providing a good contact. Some switch cleaner on the switch contacts and excercising the switches will fix this.

A component could have aged sufficiently to fail, which might be visible on the circuit board.

You've chosen a tricky machine to start with as it's quite small!

There are a lot of Youtube videos of people applying rudimentary repair methods, which are usually too good to be true. Perhaps OK as a shortcut for an experienced engineer, but not as the first approach for someone inexperienced. The unit required quite a bit of precision work when it was made, so it deserves more than firing a heat gun at it. The advantage of avoiding that approach is that you learn something about troubleshooting and are less likely to break your new purchase.

Do you have a soldering iron and a multimeter?

Well done for thinking there was a better way, and I'm sure the members here can guide you towards a repair! Welcome to the forum!

Gel38guitar · 18th Dec 2022, 6:25 pm

Yeah, i've got a multimeter and soldering gun. (However's it's a dremel cordless iron, which, i have not used. No idea how good it is.)

Thanks for the input btw! Really appreciate it.

And yeah, i was quite shocked to see how intricate the inner workings were of the sanyo. All i know is, following the wires. However, taking it apart without damaging it is another thing.

Welsh Anorak · 18th Dec 2022, 10:53 pm

Agreed - and a soldering iron is cheaper than a heat gun!
If you're new to soldering just gain some experience on an old circuit board from a scrap piece of equipment - something that's a good few years old.
As suggested above, working the record button a few times (tape present but no need for power) will clean off some dirt which might be your problem.
By all means report back - we're all happy to help!

Gel38guitar · 21st Dec 2022, 10:32 am

Here in the attachments, i've attached a photo. It looks like there's scratches in between some of the solder points. Could that be affecting the signal? (Looks like it's been filled in with something: gold?)

Honestly, i've not much idea of what i'm doing. I havent seen any cracks in the board yet. And getting the board off seems to be an issue, as there are tiny nuts holding it down. I love when i dont have proper tools.

Station X · 21st Dec 2022, 11:01 am

Looks like someone has been using a scriber to scribe between adjacent solder pads to prevent contact between them. However in doing so they appear to have cut through PCB tracks.

There are also solder whiskers coming from the large solder pad which could be short-circuiting tracks. I'd fix these problems first.

The sleeving or insulation at bottom left doesn't look too good either, but it's difficult to see what's happening from the picture.

Gel38guitar · 21st Dec 2022, 11:12 am

Also, i have a perdicament. I cant get the speaker out to remove the circuit board. I removed all the screws holding the board down, and also removed the plate holding the microphone. (All wires still intact on the board.)

Would anyone happen to have schematics for the thing? I tried looking it up earlier, but it was to no avail.

Station X · 21st Dec 2022, 11:21 am

Quote:

Originally Posted by Gel38guitar

Would anyone happen to have schematics for the thing? I tried looking it up earlier, but it was to no avail.

Sanyo M1150 appears to be a record player. Do you have the correct model number?

Gel38guitar · 21st Dec 2022, 11:41 am

Yeah. It's a tape recorder (walkman style). I actually found some schematics. But i can't make much heads or tails of it. I know ro follow the wires, but a circuit board is different from wires! (I feel maybe i'm a bit over my head, but the more i crack this thing open, the more i see and feel more comfortable. Definitely above my skillset though)😅

Gel38guitar · 21st Dec 2022, 11:55 am

Oh yay! It works! I refreshed and cleaned up some of the solder points! Works great!!

I really appreciate the input guys! Thank you so much!!!!

Uncle Bulgaria · 21st Dec 2022, 12:59 pm

That's odd, Station X - when I do a search for 'Sanyo M1150' I get loads of pictures of this, which is what I used to inform my response.

Gel38guitar - what's on the other side of the board at the point in your photograph? It looks like it could be a dual in-line package integrated circuit (DIP IC). Perhaps the scribing indicates that this IC has been replaced in the past, and the replacer wanted to avoid solder bridging adjacent pins. A wooden cocktail stick would have been the better option to clean between the solder pads!

The raised lighter green areas are copper tracks which act as the conductors. The whole board is covered in a green solder resist mask, which makes the copper appear lighter green and the dark green board remains dark. The gold colour you can see is the copper exposed by the scriber scratching through the green mask coating.

If, as Station X says, the scribing has cut through the track, then of course the relevant circuit will be broken as it's 'cut the wire'. It's possible this isn't the case, as you said some faint sound was coming through so it's perhaps more likely that the tracks have just been scratched.

If you haven't got the right tools...it's a great excuse to buy some!

DMcMahon · 21st Dec 2022, 1:37 pm

Quote:

Originally Posted by Gel38guitar

Would anyone happen to have schematics for the thing? I tried looking it up earlier, but it was to no avail.

Available from Radio Museum -

https://www.radiomuseum.org/r/sanyo_m1150m_115.html

David

DMcMahon · 21st Dec 2022, 2:11 pm

Quote:

Originally Posted by Station X

Looks like someone has been using a scriber to scribe between adjacent solder pads to prevent contact between them. However in doing so they appear to have cut through PCB tracks.

It is quite common to have solder flux (dark brown typically) between adjacent solder pads and sometimes people will scratch through it to make sure no solder shorts hiding within the flux (I have done it myself) but as Station X states who ever did the scratching they went overboard and scratched through some of the PCB tracks.

Impossible to tell from the photo if the scratched through tracks have been completely cut though, i.e. may have just cut through the top lighter green resist to expose the copper tracks.

To see if any of the scratched through tracks have been cut through completely, you will need to check for good continuity (very low resistance) either side of the possible cut through tracks, by connecting test meter to solder pads that connect to the scratched tracks.

David

DMcMahon · 21st Dec 2022, 3:03 pm

Quote:

Originally Posted by DMcMahon

Quote:

Originally Posted by Gel38guitar

Would anyone happen to have schematics for the thing? I tried looking it up earlier, but it was to no avail.

Available from Radio Museum -

https://www.radiomuseum.org/r/sanyo_m1150m_115.html

David

I had missed that you found the schematic in Post 9.

David

Station X · 21st Dec 2022, 5:47 pm

Quote:

Originally Posted by Uncle Bulgaria

Gel38guitar - what's on the other side of the board at the point in your photograph? It looks like it could be a dual in-line package integrated circuit (DIP IC).

I think it's the record/play switch which would fit in with the symptoms described.

For peace of mind I'd be inclined to solder an insulated wire strap between the points shown.

Gel38guitar · 21st Dec 2022, 5:54 pm

Quote:

Gel38guitar - what's on the other side of the board at the point in your photograph? It looks like it could be a dual in-line package integrated circuit (DIP IC). Perhaps the scribing indicates that this IC has been replaced in the past, and the replacer wanted to avoid solder bridging adjacent pins. A wooden cocktail stick would have been the better option to clean between the solder pads

I have no idea what's on the other side of the board. I couldnt get the speaker out of it's slot.

I've noticed a few things since 'fixing' the speaker earlier too.
1. I can no longer depress the record button.
2. I have sound only in mono with headphones (or is that normal, seeing there's only 1 speaker)
3. If i move the unit while playing the tape, i can lose sound altogether, or it reduces in volume. Tapping lightly will cause the sound to come back in.

Obviously, something is hanging somewhat loose that i cannot see.

Uncle Bulgaria · 21st Dec 2022, 6:02 pm

Quote:

Originally Posted by Station X

I think it's the record/play switch which would fit in with the symptoms described.

After seeing that picture of the board layout from Radio Museum, I think you've got it.

Gel38guitar:

1)You could have dislodged the mechanical latching, or you could have a cassette in the machine with the 'record protect' tag removed, preventing you from pressing the button with such a cassette inserted.
2)Headphone sound will be stereo. If you can follow the signal back from the channel you're missing (perhaps with the help of the circuit diagram and board layout drawing that David found) you will find the culprit. The record/play switch is where the smart money is at present. A can of switch cleaner is a great investment. In the short term, operating the switch a hundred times would help to break an oxide layer.
3)Yes, it sounds as if a connection is not being properly made, likely (and hopefully most simply!) the switch. Sometimes problems really are as easily fixed as that!

Gel38guitar · 21st Dec 2022, 6:38 pm

Any ideas on how i can get the speaker out? It seems to be stuck on 1 point on the right upper side. Is it just the magnet holding it in? (Wish i had a proper parts diagram as well. That'd help in taking it apart)

Graham G3ZVT · 21st Dec 2022, 6:53 pm

Quote:

Originally Posted by Gel38guitar

I've noticed a few things since 'fixing' the speaker earlier too.
1. I can no longer depress the record button.

Make sure that there is a cassette in the machine, and check that the plastic tabs at the back of the cassette are not missing.

ms660 · 21st Dec 2022, 7:34 pm

So far as I know, the machine is Mono.

The "scored" PCB track in question connects the RH switch contact of S1-1 (as viewed in the schematic) to R20 etc etc.

The "scored" track at the opposite end of the switch connects the LH switch contact of S1-3 (as viewed in the schematic) to the record/playback head and the RH contact (as viewed in the schematic) of S1-6.

The schematic shows the record/playback switch in the playback position

Lawrence.

18th Dec 2022, 12:15 pm	#1
Gel38guitar Triode Join Date: Dec 2022 Location: Putten, The Netherlands. Posts: 12	Sanyo M-1150 tape recorder (1979). Hey guys, I recently bought a used tape recorder. (See title) All of the buttons and functions seem to work fine, however, upon inserting a tape all i hear from the speaker (and headphones jack) is static. Sometimes i can make out a voice, but it's very faint. I saw a guy on Youtube using a heatgun to heat up the soldering points on the circuit board. It worked after this process. I noticed discoloration in the video on his circuit board. I have not done this as I find it very risky. Is there a better way to get the speaker/headphone ports working? And is it inded the soldering points that need warming up, or another issue maybe? (The speaker is in good condition). Thanks for any help.

18th Dec 2022, 3:04 pm	#2
Uncle Bulgaria Nonode Join Date: May 2016 Location: Cornwall, UK. Posts: 2,333	Re: Sanyo M1150 tape recorder (1979) Yes - there are numerous better ways of doing it. First, find what the problem is, which needs some deduction and logic. If the signal is being lost between the input and output, you need to narrow down where that is happening. If the man in the video had success with a heat gun, it implies there was a poor solder joint which the heat gun melted and reformed. A better way is to inspect the circuit board with a magnifying glass to look for poor joints. This could be a visible crack, or a joint that looks dull and grey rather than shiny. More likely is that the signal passes through a switch (usually play/record) which has got oxidised and dirty and isn't providing a good contact. Some switch cleaner on the switch contacts and excercising the switches will fix this. A component could have aged sufficiently to fail, which might be visible on the circuit board. You've chosen a tricky machine to start with as it's quite small! There are a lot of Youtube videos of people applying rudimentary repair methods, which are usually too good to be true. Perhaps OK as a shortcut for an experienced engineer, but not as the first approach for someone inexperienced. The unit required quite a bit of precision work when it was made, so it deserves more than firing a heat gun at it. The advantage of avoiding that approach is that you learn something about troubleshooting and are less likely to break your new purchase. Do you have a soldering iron and a multimeter? Well done for thinking there was a better way, and I'm sure the members here can guide you towards a repair! Welcome to the forum!

18th Dec 2022, 6:25 pm	#3
Gel38guitar Triode Join Date: Dec 2022 Location: Putten, The Netherlands. Posts: 12	Re: Sanyo M1150 tape recorder (1979) Yeah, i've got a multimeter and soldering gun. (However's it's a dremel cordless iron, which, i have not used. No idea how good it is.) Thanks for the input btw! Really appreciate it. And yeah, i was quite shocked to see how intricate the inner workings were of the sanyo. All i know is, following the wires. However, taking it apart without damaging it is another thing.

18th Dec 2022, 10:53 pm	#4
Welsh Anorak Dekatron Join Date: Apr 2005 Location: North Wales, UK. Posts: 6,916	Re: Sanyo M1150 tape recorder (1979) Agreed - and a soldering iron is cheaper than a heat gun! If you're new to soldering just gain some experience on an old circuit board from a scrap piece of equipment - something that's a good few years old. As suggested above, working the record button a few times (tape present but no need for power) will clean off some dirt which might be your problem. By all means report back - we're all happy to help! __________________ Glyn www.gdelectronics.wales

21st Dec 2022, 10:32 am	#5
Gel38guitar Triode Join Date: Dec 2022 Location: Putten, The Netherlands. Posts: 12	Re: Sanyo M1150 tape recorder (1979) Here in the attachments, i've attached a photo. It looks like there's scratches in between some of the solder points. Could that be affecting the signal? (Looks like it's been filled in with something: gold?) Honestly, i've not much idea of what i'm doing. I havent seen any cracks in the board yet. And getting the board off seems to be an issue, as there are tiny nuts holding it down. I love when i dont have proper tools. Attached Thumbnails

21st Dec 2022, 11:01 am	#6
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,287	Re: Sanyo M1150 tape recorder (1979) Looks like someone has been using a scriber to scribe between adjacent solder pads to prevent contact between them. However in doing so they appear to have cut through PCB tracks. There are also solder whiskers coming from the large solder pad which could be short-circuiting tracks. I'd fix these problems first. The sleeving or insulation at bottom left doesn't look too good either, but it's difficult to see what's happening from the picture. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

21st Dec 2022, 11:12 am	#7
Gel38guitar Triode Join Date: Dec 2022 Location: Putten, The Netherlands. Posts: 12	Re: Sanyo M1150 tape recorder (1979) Also, i have a perdicament. I cant get the speaker out to remove the circuit board. I removed all the screws holding the board down, and also removed the plate holding the microphone. (All wires still intact on the board.) Would anyone happen to have schematics for the thing? I tried looking it up earlier, but it was to no avail.

21st Dec 2022, 11:55 am	#10
Gel38guitar Triode Join Date: Dec 2022 Location: Putten, The Netherlands. Posts: 12	Re: Sanyo M1150 tape recorder (1979) Oh yay! It works! I refreshed and cleaned up some of the solder points! Works great!! I really appreciate the input guys! Thank you so much!!!!

21st Dec 2022, 12:59 pm	#11
Uncle Bulgaria Nonode Join Date: May 2016 Location: Cornwall, UK. Posts: 2,333	Re: Sanyo M1150 tape recorder (1979) That's odd, Station X - when I do a search for 'Sanyo M1150' I get loads of pictures of this, which is what I used to inform my response. Gel38guitar - what's on the other side of the board at the point in your photograph? It looks like it could be a dual in-line package integrated circuit (DIP IC). Perhaps the scribing indicates that this IC has been replaced in the past, and the replacer wanted to avoid solder bridging adjacent pins. A wooden cocktail stick would have been the better option to clean between the solder pads! The raised lighter green areas are copper tracks which act as the conductors. The whole board is covered in a green solder resist mask, which makes the copper appear lighter green and the dark green board remains dark. The gold colour you can see is the copper exposed by the scriber scratching through the green mask coating. If, as Station X says, the scribing has cut through the track, then of course the relevant circuit will be broken as it's 'cut the wire'. It's possible this isn't the case, as you said some faint sound was coming through so it's perhaps more likely that the tracks have just been scratched. If you haven't got the right tools...it's a great excuse to buy some! Attached Thumbnails

21st Dec 2022, 6:38 pm	#18
Gel38guitar Triode Join Date: Dec 2022 Location: Putten, The Netherlands. Posts: 12	Re: Sanyo M-1150 tape recorder (1979). Any ideas on how i can get the speaker out? It seems to be stuck on 1 point on the right upper side. Is it just the magnet holding it in? (Wish i had a proper parts diagram as well. That'd help in taking it apart) Attached Thumbnails

21st Dec 2022, 7:34 pm	#20
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Sanyo M-1150 tape recorder (1979). So far as I know, the machine is Mono. The "scored" PCB track in question connects the RH switch contact of S1-1 (as viewed in the schematic) to R20 etc etc. The "scored" track at the opposite end of the switch connects the LH switch contact of S1-3 (as viewed in the schematic) to the record/playback head and the RH contact (as viewed in the schematic) of S1-6. The schematic shows the record/playback switch in the playback position Lawrence.