Aiwa AD-F770 Belts Replacement & Idler Wheel Fix




Introduction: Aiwa AD-F770 Belts Replacement & Idler Wheel Fix

About: A technology tinkerer based in a green and usually rather damp part of the Cheshire countryside.

I recently dragged my once-beloved Aiwa AD-F770 cassette recorder from the attic with a view to putting it on eBay but soon discovered that it made a high-pitched motor whirring noise when powered up.

The fact it powered up at all was quite heartening but there was obviously a problem and this turned out to be 'melted' drive belts. This appears to be a common problem if Google search results are anything to go by, so I found a supplier (see 'Parts'), ordered the belts and did some research.

A quick Google turned up a number of YouTube videos showing how to change the belts, but I generally prefer step-by-step guides, so I thought I'd put this Instructable together to document my (as it turned out) successful repair.

As can be expected with these types of repair, the anticipated quick belt change evolved into something more time-consuming. In my case this involved a partial strip-down of the tape transport mechanism to rejuvenate a defective idler wheel and to unjam the feed side pinch roller.

This Instructable therefore details the quick-fix belts change (where the tape transport is left in place) and then covers the removal of the mechanism to get at the aforementioned idler and pinch roller. Obviously the latter will also give you access to change the belts but if you only have to change the belts, use the quick-fix method as it is easier and quicker.

It almost goes without saying that a YouTube video and a forum or two helped get this repair going. I've linked to the ones which were of most help.

Step 1: Parts and Tools



You'll need a modest set of workshop tools:

  • 0pt & 1pt Phillips screwdrivers
  • Custom screwdriver tool (if you're leaving the transport mechanism in place) - see my Instructable here. This comprises a modified clothes peg, a 0pt Phillips 1/4" screwdriver bit and a 4mm / 4BA open-ended spanner.
  • Jeweller's screwdrivers.
  • Bright work light(s)
  • Binocular magnifier (very useful)
  • Caliper (not essential but could save some guesswork)


  • Cotton buds (for cleaning gunk).
  • IPA (IsoPropyl Alcohol tape head cleaner)
  • Metal polish (eg) if you have a corroded pinch roller shaft.

Step 2: Remove the Lid and Admire the Mess Inside...

Remove the three screws on either side of the case and the two at the rear,

Remove the lid and gasp at the mess. They don't make audio equipment like this any more!

The three photos of the tape transport show where the belts were. I'd previously removed them in an effort to measure their dimensions but this turned out to be futile as they were in a melted, gungy state.

Step 3: Removing the Power Switch

To access the screws securing the rear plate of tape transport mechanism, you need to remove the power switch.

Undo the screw (marked) and gently ease out the switch as shown.

Step 4: Remove the Screws From the Rear of the Tape Transport

To remove the screws with the mechanism in-situ, you'll need a 0pt Phillips 1/4" screwdriver bit and a 4mm / 4BA open-ended spanner (see my Instructable referenced in the parts list).

The screws to be removed are circled in red on the photos. They're all the same length except the right hand one (looking from the rear of the recorder).

Unscrew them using the custom tool (or via your own method). The top screw can be removed using a conventional screwdriver.

Step 5: Remove the Tape Transport Rear Plate

Gently ease the plate away from the rear of the tape transport mechanism. This permits access for cleaning the black belt gunge...

Step 6: Clean the Motor Pulley and Flywheels

Using cotton buds and IPA (IsoPropyl Alcohol), remove the melted rubber and debris from the motor pulley and flywheels.

Change the buds frequently. The rubber deposits usually come away nicely but take your time and be thorough.

Don't be tempted to scrape away the larger deposits with your fingernails. I did and it took me longer to clean the gunk off my finger than it did to clean the flywheels. You've been warned!

Once the wheels are nice and clean, it's time to fit the belts.

Step 7: Fitting the Drive Belts

The drive belts come in two lengths. The slightly shorter one goes on the flywheels and is fitted first.

The belts should be fitted as shown in the photos. I used a plastic case opening tool I bought as part of a kit to guide the belts into place but anything small with a right angle could do at a pinch (eg) a small allen key or a bent piece of coat hanger wire. Plastic is ideal though as it's unlikely to nick the rubber of the belts and/or scratch the mechanism.

The second (longer) belt should be fitted around the flywheel first then dragged onto the motor pulley as shown.

Once you're happy the belts are fitted correctly, you can refit the back plate.

Step 8: Refitting the Rear Plate and Seeing If Everything Now Works

Offer up the rear plate and once you're happy it's in the right place, refit the screws. I started with the top screw as it's the easiest and will hold the plate in place whilst fitting the lower screws.

Remember that the long screw goes in the right hand side.

At this point, you should be in a position to power up the recorder and check you've restored it to working order. However, as mentioned in the introduction, I found that although the capstans did indeed now work as they should, the fast forward/rewind didn't and I then found the feed side capstan pinch wheel was jammed.

This sort of thing should be expected of old tape decks and their ilk and it's quite probable you'll find something similar. Tackling this requires the removal of the transport mechanism from the recorder but it's not that big a job as you will see in the next part of this exciting Instructable...

Step 9: Removing the Tape Transport Mechanism Part One

Remove the six screws securing the mechanism on the chassis.

The top two screws are 7mm long, as are the bottom screws nearest the fascia. The remaining two are 5mm long.

Step 10: Removing the Tape Transport Mechanism Part Two

Gently ease the transport mechanism out as shown in the photo. You shouldn't need to use any 'assistance' (such as levering with a screwdriver), it's just a matter of manoeuvring but make sure the attached wires aren't trapped or hooked around the circuit boards.

Once the mechanism is free, you'll have enough slack on the wires to lay it flat on top of the circuit boards. After the photo was taken I rested the mechanism on a small cushion cover to protect it and the circuit boards from mutual damage.

Step 11: Remove the Cassette Drawer

To get access to the idler wheel, you need to remove the cassette drawer. This is probably easier than it looks.

Using the photo as a guide, gently ease the top of the cassette drawer away from the brass locating spigot, first on one side, then the other.

Moving down to the hinge, do likewise to the lower spigots. My photo isn't very clear but make a note of how the lower spigot engages with the drawer - it's not very intuitive.

Next, remove the screw holding the damper in place (circled in the second photo) and remove the damper assembly.

You should now be able to remove the drawer and place it next to the transport mechanism (it's held on by wires, so you don't have too much choice!).

You now have access to (some of) the inner mechanism. What you do next depends on your circumstances and the following steps cover what I had to do, so may not apply in your case.

Step 12: Removing the Idler Wheel

This in my opinion is the only tricky bit.

The idler wheel is the one shown arrowed in the photo. This is usually where the problem lies with a non-working FF/REW issue and in my case was because the rubber periphery had hardened so it wasn't able to grip the motor pulley and hub wheels.

This is how to remove it:

Ease the sliding plate out of the way (first photo) by displacing the angled metal lever and then gently easing the plate connected to the tape heads over the black piece of plastic in the middle and to one side. Hopefully the photos make this clearer.

The idler wheel is held in place by a spring, a washer and a split washer.

Place one fine jeweller's screwdriver on the idler wheel spindle and keep it there. This does two things - it keeps the wheel in place whilst you prise the split washer gently off the spindle with the other fine jeweller's screwdriver and (most importantly) it stops the split washer, washer and spring from shooting high into the air and becoming lost forever, thus forcing an early termination of this Instructable.

Assuming this hasn't happened, place the spring and washers to one side.

Removing the idler wheel from its spindle can be done without any forcing. I was able to ease it off the spindle with a screwdriver and work it past the take up spool hub. It does come off!

Step 13: Fettling the Idler

After cleaning the wheel with some IPA, it was obvious the rubber had hardened. I read a tip on a forum where the poster had claimed success by simply twisting the rubber ring so that its outside was now on the inside, exposing fresh(ish) rubber to the outside. I tried this but it didn't work for me, so the choice was either to buy a new rubber wheel (possible source here) or increase the diameter of the current rubber wheel slightly by putting some packing next to its inner surface.

I did the latter which worked a treat. However, I'm impatient and a prudent person would of course buy a new one - after all, we're talking 1980s rubber here!

If like me you're impatient, read on...

Disassemble the wheel as shown in the photo and clean the parts with IPA.

The inner diameter of the rubber ring is 10mm, so using Pi*D I calculated the wheel's circumference as 31.4mm.

(The dimensions of the rubber ring are: OD: 13mm; ID: 10mm; thickness: 1.65mm; height: 2.4mm).

I cut a strip of self-adhesive metal tape* (purchased from Aldi years ago) 31.4mm long and 2.2mm (approx) wide and placed it on the idler as shown. Metal tape is good as it is relatively stiff and less likely to buckle than say, insulation tape. The tape was 0.3mm thick so adds 0.6mm to the idler wheel diameter.

* this tape is quite thick, so if yours is thinner I'd suggest doubling the length and doing a double wrap.

Refit the rubber ring with its fresh side outwards (see above). Before refitting it (a reversal of the last step - don't forget to guard against spring and washer escape attempts), add a very light coating of silicone grease to the spindle and clean (if you haven't already) the fast fwd/rew motor pulley with IPA.

Step 14: Fettling the Feed Pinch Roller

The feed capstan assembly is circled in the first photo. As it incorporates a tape guide, measure the length of the screw protruding at its pivot point so when reassembling, you can get the tape guide in the correct place. An alternative (which I used) was to measure the height of the underside above the chassis (shown on the photo). In my case this dimension was 14.45mm.

If you don't have access to a caliper, count the number of visible threads where the nut screws on. On reassembly, you can then tweak the height when playing a tape with lots of treble on it. The nut is accessible from the outside.

Another thing to do before removal is to note carefully where the two springs attach at either end. Take some photos just in case.

Removal is simply a matter of undoing the nut and sliding the assembly off the post.

Once removed, you'll then have to disassemble the roller itself. To do this, I found a broken drill bit of smaller diameter than the roller shaft and drifted the shaft out using light taps from a small hammer.

The shaft came out a little grudgingly and the photo shows why.

Clean the roller with IPA and the shaft with metal polish. Again, a very light film of silicone grease should be applied to the shaft on reassembly (take care not to get any on the rubber of the pinch wheel as it's very problematic to remove). Check the wheel now turns freely.

Refit the assembly to the transport and adjust the height using the measurement you took before disassembly..

Step 15: Refitting the Transport Mechanism

Refit the cassette holder - start at the top by re-engaging the brass spigots and then re-engage the spigots at the other end (you have to close the holder's drawer slightly to get the holes and slots lined up).

Refit the damper.

At this stage, I'd check everything you've worked on is now functional - this is a bit risky as you have to make sure the transport isn't touching the circuit boards etc. - rest it on some insulating material and make sure the moving parts (mainly the flywheels) are free to move. Insert a sacrificial cassette and power up the deck. Check fast forward and rewind both work and then try play. If all is well proceed as below. If not, I wish you good luck in your fault tracing!

Switch off power and remove the plug from the wall outlet.

The transport can now be refitted into the tape deck - this should be done carefully with no forcing. Make sure none of the attached wires get snagged and pay attention to where the tape head wiring fits in a slot under the cassette drawer hinge.

It should just go straight in but if you struggle, don't worry - take your time and it will!

Step 16: Testing (and a Few Thoughts)

Once fully reassembled, it's time for testing.

As before, I'd start with a sacrificial cassette but if all is well, you can dig out your old tape collection and reacquaint yourself with a previous life.

Once you're happy with the height of the feed pinch roller, dob a bit of clear nail varnish on the fixing nut to stop it wandering over time.

I'd forgotten just how good this deck is and I'm now reconsidering whether eBay is the right option for this lovely piece of kit. Having said that, track selection requires patience.

The thing I find interesting is that these (mostly) thirty to forty year old tapes play back very nicely (once run through backwards & forwards) and despite the advice of the professional tape recording community, don't appear to leave their oxide all over the tape heads and capstans.

I hope you found this Instructable informative & helpful and I welcome all constructive comments!

Be the First to Share


    • Clocks Contest

      Clocks Contest
    • Make it Glow Contest

      Make it Glow Contest
    • Block Code Contest

      Block Code Contest



    9 months ago

    I was asked a few days ago to help a prospective buyer by suggesting a few questions to ask sellers of the ADF770. Here's my response, which will hopefully be of interest:

    Questions and considerations
    I suppose it's stating the obvious but the big issues with the 770 are its age and lack of spares. I bought mine over 42 years ago and it staggers me it's still playable. I only have the one deck so I can only advise regarding what's gone wrong with mine.

    The drive belts needed replacing, the bearings of the capstan rollers needed cleaning and lubricating and the tape FF/REW idler wheel tyre had hardened and needed fettling. The tape transport path needed cleaning and I also realigned the tape heads. I considered demagnetising the rec/replay head but decided against it as it sounded OK (I didn't want to disconnect the heads electrically which is normally required when demagnetising). I also checked the capstan motor speed. I don't have any test equipment for measuring wow & flutter, so I had to rely on my hearing but thankfully it sounds good in that regard.

    Electronically, I haven't had a failure, other than a burnt-out fuse resistor I caused myself when being sloppy with my test leads(!) and I've not seen any issues with dry electrolytic capacitors. That's for a deck which has not been abused and stored in a reasonably dry, benign environment.

    Considering a deck with unknown history, you can reasonably expect to have to do the above as a minimum. Mechanically, you could also be faced with electrically noisy switches, broken push buttons, worn tape heads, seized motors, eccentric capstan rollers, stiff bearings etc. Electrically, as the internal wiring resembles an explosion in a spaghetti factory, I imagine there's the possibility of snapped or trapped wires caused by previous repair attempts as well as circuit failures caused by damp and/or old age etc.

    I think your options are limited when it comes to what you could reasonably do when faced with combinations of the above. The big issue is the lack of any spares. Even if you're lucky and acquire another 770 as a sacrificial spare, it's likely most of the rubber parts you'll need are unusable on both decks, due to age. Fortunately you can still source the drive belts. I've not (as yet) found a source for capstan roller tyres. The new idler wheel tyre I bought (advertised for the 770) was larger than the original and jammed the mechanism. I ended up treating the original tyre with platen cleaner and weakening a spring on the one of the spools (the feed spool, I think). This has worked to date. My takeaway experience is definitely 'caveat emptor' and be prepared for disappointment!

    Electronically, there are no surface mount components (of course), so all the discrete parts, such as transistors, diodes, resistors etc. are probably replaceable with modern parts. The display and ICs are a different matter - they appear to be custom parts for ADF decks and I think the only spares these days would be ones you can salvage from another deck.

    In the light of the above, what questions should you be asking a seller? Well, you can probably formulate your own after reading the above but I would definitely want to know: How many owners has the deck had? How's it been stored? When was it last used? Did it work fully on that occasion and if not, in detail what didn't work? What hasn't been tested? Is the deck a 110v or 240v ac version? Has it ever been repaired? If so, is there any accompanying paperwork? Is there more than one deck on offer?

    I'd be very wary about paying top dollar for a deck that hadn't been fully tested and available with a warranty, although I'd be very surprised if such a deck existed!

    If you're keen on tape decks, please don't let me put you off - I've focussed on the negatives for obvious reasons. I still occasionally listen to some of my old recordings and it's always a joy*!

    * tempered by having to keep half an eye on the take up spool function to avoid tape jams!!


    1 year ago

    Dear, do you know what a problem may be for a not working counter section at powering the 770? Just bought it here:

    It is said: Deck powers, no counter, no fw/rw, play/rec. Does changing belts affects viewing counter’s 00,00 at powering or it is another part to be replaced?
    Seller said never open the deck, however do not know about previous owners.
    Any advise would be helpful.

    Thank you, and greetings, Ed


    Reply 1 year ago

    I've not played with the counter part of the 770 but I'm pretty sure the counter is fed from pulses output from the take-up reel, so if the belts are inoperative, the counter would definitely not increment.
    Good luck!


    Reply 1 year ago

    Thank you dear Night, also for the very nice instructable I hope to be able to follow step by step!
    Will look inside of the 770 end of January with that hope the not illuminated counter section and transport disfunction are all due to faulty belts. Will give news then.
    Many thanks again, and all best!


    Reply 1 year ago

    Hi Ed - good luck with the investigation. Maybe it's a language thing and I misunderstood what you originally said but if the counter section isn't illuminated, that won't be fixed by a change of belts. An illuminated but stuck at 0000 counter would be (most likely).


    Reply 1 year ago

    Hi Night, and thank you kindly, this helps. Yes, a french speaking originally here, trying my best in English. That’s why gave a link above to the purchased item (hope you can view the pics of the 770 powered with no illuminated counter section).
    So, may that comes from not working motors, a faulty valve behind, other faulty parts?
    Any suggestions would be helpful, and thank you once;
    Greetings, Ed


    Reply 1 year ago

    Hi Ed! I should have read your original post more carefully! I didn't notice the tape counter wasn't illuminated on my deck when the belts were broken, but that doesn't mean it was. I think the most likely cause though is a fault in the circuitry driving that part of the display, which could be simple to fix or in the worst case, irreparable due to the lack of spares. It's possible, however, the display doesn't illuminate because the reel movement sensor isn't providing pulses to the display driver circuit on power-up (I don't think this is very likely though). I suppose the usual process applies - fix the faults you know about (ie) the belts and then see what's left. I'll help if I can!


    Reply 1 year ago

    Hi Night, and thank you, ok belts fist.
    (Meanwhile asked the seller to check if the motors are working, do they spin when pressing Play, FF, RW? (If they do, then it needs new belts.)
    Got an answer: «Checked again.
    As already described in the auction, no function with Play, FF, RW.
    Motor noise can be heard, right capstan rotates.»)
    Guess good news, Night; any thoughts?
    Go for belts.


    Reply 1 year ago

    Hi Mike, and hope you’re doing fine. (Friday February 4th Edit => Source/Monitor switch arm picture (arm/switch junction broken); And an overall inside view (pictures 6 - 7 added) => No visible capacitors leakage (or falling parts/particules except the small plastic arm head).

    In short (Pictures 1 - 7 here attached): (Motor says: 21 July 1983)


    - Motor runs from powering, with both melted belts. But seems they are two =>

    (Pressing upper right in cassette holder => red light/metal tape, but no rw/fw function.)


    - Sticked PLAY button, other ones feel softer.

    - Source/Monitor switch acts like a push-in only, not as a switch (broken arm).

    (Picture 6)

    - Input tested from a CD player signal: In Source mode Record at MAX => level looks quite low (to me).

    - 3 color (Red-Rose-White) wire looks disconnected (from headphones?) Phones input death quiet. (Thank you checking yours where this wire goes?)

    - And last, have to fingerpush to eject cassette. Why so?

    With hope to get advises from you on above described, still doing first belts change. Hope new belts would run transport lights/fw/rw, yes?

    (And checking the full great tutorial, i thank you once.)



    1_Tricolor cable.JPG2_Tricolor cable to Phones.jpg3_Tricolor to Phones.JPG4_Monitor switsh - Low source level.JPG5_Fingerpush to eject.JPGBroken switch arm.JPGOveral-No caps leakage.jpg

    Reply 1 year ago

    Hi Ed! I'll help if I can. Best to sort out the belts first, then see what else doesn't work. Like I said before, I'd be surprised if the belt repair fixes the non-working tape counter display. I'll be happy to take some more photos for you - the ones attached are of the cut wiring you mentioned and of the switch attached to the monitor button. Cheers and good luck! Mike

    Play - Off -Rec wiring.jpgMonitor switch.JPG

    Reply 1 year ago

    Thank you kindly Mike, just found both pictures, and if you please check above updated my yesterday's post. Fine day! Ed


    Reply 1 year ago

    Good to see you found the reason the Monitor button doesn't work as it should. I'm not sure what adhesive to use as I think it's a type of plastic hard to glue. In your shoes, I'd probably try epoxy and maybe use a small metal dowel drilled longitudinally to give it some strength.
    Can you describe the sticky 'Play' button issue? Is it hard to press? Does it stick down after you've pressed it?
    The cassette drawer eject is damped with a small friction mechanism near the hinge (see photo). It's very likely the cause of the sticking drawer is due to the damper being dirty/misaligned or damaged. Either that of there's something fouling the hinges. I would suggest ignoring the first part of my Instructable and follow the second part, where I remove the transport assembly from the case. You'll then have access to all the moving parts. Just be very careful not to break or trap any wires when reassembling (it's easily done) and don't use force - the mechanism will go back in without difficulty when offered correctly!
    Most faults you'll find with a machine this old will be mechanical. I've been lucky (so far) that I've not had any circuitry to fix (apart from a resistor I burned out through sloppiness on my part). All the electrolytic caps on mine appear to be OK (which are the most likely components to suffer through old age) and I'm glad to hear yours too appear OK.

    Side showing damper.jpg

    Reply 1 year ago

    Hi Mike, and thank you. For the glue i only was going with a second glue, but will try to find an epoxy first, indeed. All buttons (attached short video) clics, less FW, not the PLAY. It is hard to press, it doesn't move as i feel.
    So, would you suggest bottom four screws opening carefully / see what may sticks inside - old grease? (photo attached) and a here link to Darren's 660 => Please, see Minute 4:00 to 5:20)
    Back to the cassette eject problem soon, secondly. With greetings, Ed

    Suggest bottom 4 screws opening.JPG

    Reply 12 months ago

    Hi It's actually 7 screws you'll have to undo to remove that access panel. That will only give you access to the underside of the switch board but hopefully you'll see how to access the top part from there (I've not disassembled that part, so I can't advise from experience). With a bit of luck, you'll find some debris is fouling the switches. If you're unlucky (and more likely), the lack of movement will be because the switch underneath the button is jammed. They look like fairly common switches though and if you've got an old VCR or similar up in an attic, you should have some to harvest and reuse as replacements. I haven't opened the .mov file as I'm a bit paranoid about downloads - is there a YouTube link or similar?.


    Reply 12 months ago

    Thank you Mike, meanwhile i was there (under the 7 screws), gently brushed/de dusted and applied lightly IPAlcohol at buttons ends, and feel clics better but it will need more with a new grease, i guess; Cleaned a bit all over too, drawn up the front panel as shows the 660's service manual. And saw something bad far right on the level screen - a brown burned mark. Something to do with counter section? Also, inside my 770 i saw an unplugged male socket (about i'd like to ask you see into yours 770), and so attached here are 2 pictures). However can't see a floating wires pin to connect to. Next i'd try the belts replacement and if unit runs, next would be the 2nd part of your tutorial. Thanks, and greetings, Ed

    That socket.JPGUpper right on the level meter.JPG

    Reply 12 months ago

    I pressed 'Reply' and my comment disappeared...(I think). Here's another go and it's a little more condensed. Well done with sorting the stuck buttons. The brown burn mark is visible on mine and is a mark left by the 'getter' or equivalent during manufacture (this article in Wikipedia explains - The unplugged male socket is a test connector (I suspect) - it's not connected on mine also (see photo). Good luck with the belts!


    Question 1 year ago on Step 16

    I just went through and replaced the idler wheel and belts. Cleaned up old grease and replaced. But .. the head unit will not engage the tape. It stays motionless when i hit PLAY. It was stiff before, but now it doesn't move. I assumed it was sticky grease but.. ? Any ideas?


    Answer 1 year ago

    What happens when you power the machine up without a tape in and you press the microswitch in the top right hand corner? The feed spool should rotate clockwise for 1 second or so and the Tape Type light should illuminate.


    Reply 1 year ago

    With the door closed i power on and the there is a loud click. The ADMS light comes on for about 1 full second then clicks and the ADMS light turns off. When i press on the lever in the upper right (lid is off so i am pressing from above) there is a quick whirring sound of about 1 second (the advance probably), the tape type "metal" appears on the main display and the Tape Indicator LED illuminates in red next to the word " metal".


    Reply 1 year ago

    There is also a quick, "whirring" sound of about 1 second when i depress the contact. That sounds like the advance.