Teac A3440 DC motor failure . - UK Vintage Radio Repair and Restoration Discussion Forum

NorfolkDaveUK · 2nd Mar 2019, 3:13 pm

Can someone tell me what the value of the burned out part in this motor is please (see pic, i know its a resistor ..lol) . Also , what may have caused this . I`ve found the symptom not the cause I believe (see pic). It was running fine , then had a little wobble , and the tape slowed , then it started again , then it just stopped for good . I`m wondering if it just got stuck and burned out ?

Thanks as always .
David.

NorfolkDaveUK · 2nd Mar 2019, 3:21 pm

I`ve just found a load of belt "goo" on the control board , so I`m better that at some point this motor had been ceased and almost burned out because of belt "goo" gamming it up . Someone has cleaned all that out , but not had a look in the motor, its worked for a min and then he`s sold it to me . I just need to replace the cap and the resistor and I should be good I think . Anyone know the value ? wattage ?

NorfolkDaveUK · 2nd Mar 2019, 3:34 pm

this would help wouldnt it , and i meant inductor , not resistor...

ms660 · 2nd Mar 2019, 3:57 pm

It could be a choke, what's its core material, is there a copper wire coil in its construction?

Lawrence.

NorfolkDaveUK · 2nd Mar 2019, 4:02 pm

Yeah it is an inductor choke bud. I think its 10uh after having a look round google. Seems its a pretty common fault. I think I`m going to put a wire wound one in there instead. Just waiting for RS to finish updating their website ....

TIMTAPE · 3rd Mar 2019, 8:35 pm

Motor failure in these machines can be due to an old belt stretching, folding over and jamming the motor. If you're lucky, the burned out choke is the only fault but I'd check the armature for signs of overheating, shorted turns. Be careful reassembling the motor to not damage the brush arms.

I suspect these small DC capstan motors can also be stressed due to playing of sticky tapes.

NorfolkDaveUK · 4th Mar 2019, 1:25 am

Thanks Tim, I`m finding lumps sticky belt through the machine so I`m pretty sure the cause was the motor jamming up on sticky tape goo and then someone "got rid quick" kinda thing . Lets hope you are right about the choke !

Radio Wrangler · 4th Mar 2019, 2:43 pm

What is the melted and nasty stuff on the brush arms?

It looks beyond coincidence that belt fallout hits the arms exactly and only. Some sort of plastic support that's melted?

David

TIMTAPE · 4th Mar 2019, 4:24 pm

From memory, rubber strips bonded to the brush arms, maybe to dampen bouncing of the brushes on the commutator. It looks like the brushes/arms have overheated and melted the rubber. All of which places a question mark over more than just the choke, hence my previous comment.

NorfolkDaveUK · 5th Mar 2019, 12:50 pm

It's as Tim says, it's rubber and it's not melted it's turned to "goo". I'll be replacing it as best I can. It dampens the bouncing of the brushes and to be fair it is still doing it, but it needs to go for sure.

NorfolkDaveUK · 5th Mar 2019, 1:42 pm

OK so I changed the choke , and the cap , which wasnt bipolar surprisingly , it ran for about a second , then blew the fuse and the cap . On checking the windings , I get a resistance of 1.0 - 2.4 all the way around apart from in one place which is dead short

DangerMan · 5th Mar 2019, 3:44 pm

Have a good look at the commutator through a magnifying glass.
It is not unknown for small slivers of metal to be drawn across the gaps by the brushes and causing the short that you can measure. Alternatively, just clean out the gaps and remeasure it in case one of them is choked with carbon dust.
Are there any small ceramic capacitors mounted on the armature, across the commutator gaps?

TonyDuell · 5th Mar 2019, 4:40 pm

Do the windings look burnt? Normally shorts come if the insulation (enamel) gets hot enough to burn off so the wires then touch. If you are feeling brave, try disconnecting the wires from the affected commutator segments and seeing if it's the winding or commutator that's shorted.

In my limited experience open-circuit windings are more common than short circuits in these small motors.

I have an old HP9125 plotter. This is the plotter for the HP9100, HP's first (desktop) calculator, so not surprisingly it's interetsting to me. Both motors had open-circuit windings. With nothing to lose I took them apart (I made keepers to go in the field magnets in place of the armature, but that may not be necessary with modern permanent magnet fields) and rewound them.

If you decide to attempt a rewind, the important things to note are :

How many 'slots' each winding spans.

Where the ends of a winding go (maybe to adjacent commutator segments, maybe not and how the segments relate to the slots the winding goes in)

How many turns and in which direction.

It took me a couple of hours to rewind each 7 pole armature in that plotter. Well worth it for such a rare unt.

NorfolkDaveUK · 5th Mar 2019, 9:23 pm

thanks guys , I manages to source another motor for £80 so i went with that , I really dont want to mess with the other one too much for fear of killing the board too which is currently still outputting voltage to the board, its giving it 30v into a 24v motor , but i dont think thats too much of an issue when there is no load on it . Once there is a load that should drop quite a bit i should think

Quote:

Originally Posted by DangerMan

Have a good look at the commutator through a magnifying glass.
It is not unknown for small slivers of metal to be drawn across the gaps by the brushes and causing the short that you can measure. Alternatively, just clean out the gaps and remeasure it in case one of them is choked with carbon dust.
Are there any small ceramic capacitors mounted on the armature, across the commutator gaps?

no caps across the gaps and I`ve cleaned them out pretty good as far as i can tell .

NorfolkDaveUK · 11th Mar 2019, 10:24 pm

Ok so I got the motor problem sorted out , got a very good motor , had to replace a transistor on the speed board , and thats now doing as it should . Happy days.

Now though , the play button wont work . FFW and REW are fine , but PLAY is not having it at all . Looking at the schematic , its a flip flip , so the chances are , either a diode or a transistor bought it when the motor fuse blew , would that be a viable theory ?

TA!
Dave

ms660 · 12th Mar 2019, 12:44 pm

Check the the flip flop collector voltages, when play is pressed the collector of Q701 should go high and the collector of Q702 should go low, if that's ok it might be worth checking around Q718 to make sure it's not supplying an override voltage to cut off the play relay driver, the capstan solenoid driver and blocking off the operation of the brake solenoid .

Lawrence.

NorfolkDaveUK · 13th Mar 2019, 11:07 am

Thanks Lawrence, it seems to be a bit more complicated than that . If I leave the unit sitting for a while and then go back and forth from ffw to play a few times and it`ll start playing fine , and keep playing from there on in until I unplug it from the mains again. Once I do that and plug it in again , then I have to let it sit a while and go from ffw to play a few times before it`ll start to work again and again once it does it will continue working . All a bit strange really.

ms660 · 13th Mar 2019, 11:59 am

It might be worth doing some voltage checks if the solenoids etc don't kick in when the play button is pressed, I assume the capstan motor is functioning in fault mode.

Lawrence.

NorfolkDaveUK · 14th Mar 2019, 1:21 am

Yeah capstan is ok . FFw is ok and Rew is ok . Just play is having the issue . Once it starts working it works from then on it , like I say until I remove power then the palarva starts over .

I`ll check the voltages in the morning I`ve had one heck of a rubbish day

ms660 · 14th Mar 2019, 11:10 am

There's mention of a similar problem on page 10 in this article:

http://g4cnh.com/public/Teac%20A3440...0circuitry.pdf

Lawrence.

2nd Mar 2019, 3:13 pm	#1
NorfolkDaveUK Banned Join Date: May 2018 Location: Norwich, Norfolk, UK. Posts: 605	Teac A3440 DC motor failure . Can someone tell me what the value of the burned out part in this motor is please (see pic, i know its a resistor ..lol) . Also , what may have caused this . I`ve found the symptom not the cause I believe (see pic). It was running fine , then had a little wobble , and the tape slowed , then it started again , then it just stopped for good . I`m wondering if it just got stuck and burned out ? Thanks as always . David.

2nd Mar 2019, 3:21 pm	#2
NorfolkDaveUK Banned Join Date: May 2018 Location: Norwich, Norfolk, UK. Posts: 605	Re: Teac A3440 DC motor failure . I`ve just found a load of belt "goo" on the control board , so I`m better that at some point this motor had been ceased and almost burned out because of belt "goo" gamming it up . Someone has cleaned all that out , but not had a look in the motor, its worked for a min and then he`s sold it to me . I just need to replace the cap and the resistor and I should be good I think . Anyone know the value ? wattage ?

2nd Mar 2019, 3:34 pm	#3
NorfolkDaveUK Banned Join Date: May 2018 Location: Norwich, Norfolk, UK. Posts: 605	Re: Teac A3440 DC motor failure . this would help wouldnt it , and i meant inductor , not resistor... Attached Thumbnails Last edited by NorfolkDaveUK; 2nd Mar 2019 at 3:50 pm.

2nd Mar 2019, 3:57 pm	#4
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Teac A3440 DC motor failure . It could be a choke, what's its core material, is there a copper wire coil in its construction? Lawrence.

2nd Mar 2019, 4:02 pm	#5
NorfolkDaveUK Banned Join Date: May 2018 Location: Norwich, Norfolk, UK. Posts: 605	Re: Teac A3440 DC motor failure . Yeah it is an inductor choke bud. I think its 10uh after having a look round google. Seems its a pretty common fault. I think I`m going to put a wire wound one in there instead. Just waiting for RS to finish updating their website ....

3rd Mar 2019, 8:35 pm	#6
TIMTAPE Octode Join Date: Jul 2006 Location: Perth, Western Australia Posts: 1,969	Re: Teac A3440 DC motor failure . Motor failure in these machines can be due to an old belt stretching, folding over and jamming the motor. If you're lucky, the burned out choke is the only fault but I'd check the armature for signs of overheating, shorted turns. Be careful reassembling the motor to not damage the brush arms. I suspect these small DC capstan motors can also be stressed due to playing of sticky tapes.

4th Mar 2019, 1:25 am	#7
NorfolkDaveUK Banned Join Date: May 2018 Location: Norwich, Norfolk, UK. Posts: 605	Re: Teac A3440 DC motor failure . Thanks Tim, I`m finding lumps sticky belt through the machine so I`m pretty sure the cause was the motor jamming up on sticky tape goo and then someone "got rid quick" kinda thing . Lets hope you are right about the choke !

4th Mar 2019, 2:43 pm	#8
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,868	Re: Teac A3440 DC motor failure . What is the melted and nasty stuff on the brush arms? It looks beyond coincidence that belt fallout hits the arms exactly and only. Some sort of plastic support that's melted? David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

4th Mar 2019, 4:24 pm	#9
TIMTAPE Octode Join Date: Jul 2006 Location: Perth, Western Australia Posts: 1,969	Re: Teac A3440 DC motor failure . From memory, rubber strips bonded to the brush arms, maybe to dampen bouncing of the brushes on the commutator. It looks like the brushes/arms have overheated and melted the rubber. All of which places a question mark over more than just the choke, hence my previous comment.

5th Mar 2019, 12:50 pm	#10
NorfolkDaveUK Banned Join Date: May 2018 Location: Norwich, Norfolk, UK. Posts: 605	Re: Teac A3440 DC motor failure . It's as Tim says, it's rubber and it's not melted it's turned to "goo". I'll be replacing it as best I can. It dampens the bouncing of the brushes and to be fair it is still doing it, but it needs to go for sure.

5th Mar 2019, 1:42 pm	#11
NorfolkDaveUK Banned Join Date: May 2018 Location: Norwich, Norfolk, UK. Posts: 605	Re: Teac A3440 DC motor failure . OK so I changed the choke , and the cap , which wasnt bipolar surprisingly , it ran for about a second , then blew the fuse and the cap . On checking the windings , I get a resistance of 1.0 - 2.4 all the way around apart from in one place which is dead short

5th Mar 2019, 3:44 pm	#12
DangerMan Heptode Join Date: Jul 2009 Location: Stoke-on-Trent, Staffordshire, UK. Posts: 719	Re: Teac A3440 DC motor failure . Have a good look at the commutator through a magnifying glass. It is not unknown for small slivers of metal to be drawn across the gaps by the brushes and causing the short that you can measure. Alternatively, just clean out the gaps and remeasure it in case one of them is choked with carbon dust. Are there any small ceramic capacitors mounted on the armature, across the commutator gaps?

5th Mar 2019, 4:40 pm	#13
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,208	Re: Teac A3440 DC motor failure . Do the windings look burnt? Normally shorts come if the insulation (enamel) gets hot enough to burn off so the wires then touch. If you are feeling brave, try disconnecting the wires from the affected commutator segments and seeing if it's the winding or commutator that's shorted. In my limited experience open-circuit windings are more common than short circuits in these small motors. I have an old HP9125 plotter. This is the plotter for the HP9100, HP's first (desktop) calculator, so not surprisingly it's interetsting to me. Both motors had open-circuit windings. With nothing to lose I took them apart (I made keepers to go in the field magnets in place of the armature, but that may not be necessary with modern permanent magnet fields) and rewound them. If you decide to attempt a rewind, the important things to note are : How many 'slots' each winding spans. Where the ends of a winding go (maybe to adjacent commutator segments, maybe not and how the segments relate to the slots the winding goes in) How many turns and in which direction. It took me a couple of hours to rewind each 7 pole armature in that plotter. Well worth it for such a rare unt.

11th Mar 2019, 10:24 pm	#15
NorfolkDaveUK Banned Join Date: May 2018 Location: Norwich, Norfolk, UK. Posts: 605	Teac 3440 no play Ok so I got the motor problem sorted out , got a very good motor , had to replace a transistor on the speed board , and thats now doing as it should . Happy days. Now though , the play button wont work . FFW and REW are fine , but PLAY is not having it at all . Looking at the schematic , its a flip flip , so the chances are , either a diode or a transistor bought it when the motor fuse blew , would that be a viable theory ? TA! Dave

12th Mar 2019, 12:44 pm	#16
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Teac A3440 DC motor failure . Check the the flip flop collector voltages, when play is pressed the collector of Q701 should go high and the collector of Q702 should go low, if that's ok it might be worth checking around Q718 to make sure it's not supplying an override voltage to cut off the play relay driver, the capstan solenoid driver and blocking off the operation of the brake solenoid . Lawrence. Last edited by ms660; 12th Mar 2019 at 1:12 pm. Reason: addition

13th Mar 2019, 11:07 am	#17
NorfolkDaveUK Banned Join Date: May 2018 Location: Norwich, Norfolk, UK. Posts: 605	Re: Teac A3440 DC motor failure . Thanks Lawrence, it seems to be a bit more complicated than that . If I leave the unit sitting for a while and then go back and forth from ffw to play a few times and it`ll start playing fine , and keep playing from there on in until I unplug it from the mains again. Once I do that and plug it in again , then I have to let it sit a while and go from ffw to play a few times before it`ll start to work again and again once it does it will continue working . All a bit strange really.

13th Mar 2019, 11:59 am	#18
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Teac A3440 DC motor failure . It might be worth doing some voltage checks if the solenoids etc don't kick in when the play button is pressed, I assume the capstan motor is functioning in fault mode. Lawrence.

14th Mar 2019, 1:21 am	#19
NorfolkDaveUK Banned Join Date: May 2018 Location: Norwich, Norfolk, UK. Posts: 605	Re: Teac A3440 DC motor failure . Yeah capstan is ok . FFw is ok and Rew is ok . Just play is having the issue . Once it starts working it works from then on it , like I say until I remove power then the palarva starts over . I`ll check the voltages in the morning I`ve had one heck of a rubbish day

14th Mar 2019, 11:10 am	#20
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Teac A3440 DC motor failure . There's mention of a similar problem on page 10 in this article: http://g4cnh.com/public/Teac%20A3440...0circuitry.pdf Lawrence.