Author Topic: NAD 6130 Cassette Deck Repair (Read 6028 times)

Smoky · « **on:** March 16, 2020, 02:30:28 am »

Here's the next electronics repair, a NAD 6130 cassette deck.

This NAD gear comes from an original owner that still plays his collection of hundreds of tapes!

I was also handed an original copy of the service manual too

When I plugged the player into my Variac, I noticed that the Recording Level Display was pegged.

I could also hear a slight sluggish groaning sound coming from a motor.

Let's take a peek inside and see what we find!

The first thing discovered was this spring stuck to the side of the chassis with clear Scotch tape. Again, someone has been inside here before me. I didn't ask when the last time this tape deck was played. Maybe it played without it in place?

Here's a shot of the chassis. It appears very clean with no burn marks anywhere on the boards. There are several fuses and they all test good.

The cassette transport has a motor with the same triangle trademark found on components in a recent NAD 3150 amplifier repair. It's Matsushita/Panasonic's trademark from the 1950's.

The gears in the transport appear to be in very good condition too, but when you take a close look at the pulleys, you can see rubber particles everywhere. It's time for a belt replacement. Maybe they are getting worn-down and starting to bind/slip making the motor work overtime and causing it to groan?

I also see an area of the transport where a spring is slightly dislodged:

...and look at this! Here's the location where I think that loose spring found taped to the chassis belongs:

Bd139 mentioned in the NAD amplifier repair that those green blob capacitors are microphonic. There's about 30 of them in here. What I plan to do is to remove a couple of them and attach them to my oscilloscope and then tap them with a pencil to see if it affects the trace. I'll use the little Tektronix 310 tube scope repaired not long ago

If they are microphonic, they'll have no right being in this tape deck!

Now this isn't a very "high-end" model. It's best frequency response is when using a metal tape (40Hz-17kHz +/- 3dB).

I also will try to make a "test-tape" with my Nakamichi LX-5. I've read where a certain frequency is recorded to a cassette tape and that tape is used to align the "speed" of the drive.

Also, if anyone knows what would be the best brand/type of grease to use on these plastic gears, please let me know. All of the old grease is going to be flushed-out ...and a hint where to buy good belts for it.

I read a maintenance manual for a Garrard turntable. It specified 7 different greases to use in it!

That's it for tonight. I'm going to finish the day reading a few pages of the service manual

And since Fedex/Kinkos is just a block from the house, I'll have the schematics scanned in Hi-res and post them here too.

SpecialK · « **Reply #1 on:** March 16, 2020, 03:38:27 am »

I am a little surprised that belt is still intact. I've seen belts and pinch rollers of that vintage where the rubber turns to goo.

floobydust · « **Reply #2 on:** March 16, 2020, 05:07:35 am »

A very common problem with cassette decks is the record-play switch contacts getting old and oxidized.
I apply a lot of contact cleaner and work them by switching them back and forth 20x with a small screwdriver tugging on the arm, back and forth. Not with a tape inside either, it will get erase glitches. This usually calms down oscillating or a dead channel.

The other common repair is cleaning the clutch, if take-up tension is low. It's just an IPA soak and dry.

I use a tiny bit of plastic safe grease, Molylube, you can check it became popular for VCR transports. I use syn motor oil 10W20 on the motor and capstan bearings but keep the chemicals away from the rubber (belt, pinch roller, idler). Alcohol on a belt does dry it out so I use a q-tip with IPA on the pulleys.

MG 408A Rubber Renue is great for hard pinch rollers and rubber idler wheels (but not belts!).
If you adjust the motor speed (trimpot hole at the back) careful not to short it and ground it to the case, that can cause drama.

Smoky · « **Reply #3 on:** March 16, 2020, 06:50:21 pm »

Thank you FloobyDust and SpecialK!

I found this website that lists several NAD cassette deck model's belt kits but not the 6130:

https://www.vintage-electronics.net/nadbeltkits.aspx

The part numbers for the belts in the 6130 are:

KD4005 (Belt)
MD4017 (Drive belt)
MD4003 (Auto belt)
G44022 (Counter belt)

I sent an e-mail to the company to see if they could cross over these numbers to their other NAD models.

They do list a 6125 on their website, which is a four-belt kit. It also has a mechanical counter, so, I'll cross my fingers

What I was able to do was to use my finger to turn the brass pulley on the motor without touching the belts. One of the belts would occasionally slip while the pulley turned. All of the belts feel really loose like they've lost their tension.

FloobyDust, someone also recommended the MG Chemicals Rubber Renue but to follow it with this product to remove the "Wintergreen oil" residue:

https://hifiheaven.net/shop/American-Recorder-Technologies-S-721H-2-Professional-Tape-Head-Cleaner

More to come!

Smoky · « **Reply #4 on:** March 17, 2020, 12:04:01 am »

I got a reply from Bob at www.Vintage-Electronics.net regarding the cassette deck belts.

He says that he doesn't have the belts by NAD part number for the 6130, so he says what I need to do is measure them.

He has seven pages of belts in many, many sizes broken down by shape. He has a page showing how to measure them too.

There are two ways to measure an old belt and one much choose the next smaller size down from that to take into account the "stretch" of the old belt.

I'm guessing it would be more accurate to cut the old belt than to leave it looped?

Here is a scan of the NAD 6130 schematic:

NAD6130Schematic.pdf (2578.84 kB - downloaded 232 times.)

And parts:

NAD6130Parts1.pdf (1444.43 kB - downloaded 296 times.)

NAD6130Parts2.pdf (713.29 kB - downloaded 154 times.)

Smoky · « **Reply #5 on:** March 19, 2020, 03:11:38 am »

Hey guys, I just wanted to show you the location where that loose spring actually goes!

There are 18 springs in this cassette deck's transport. Since the loose spring is a "V" shape, I was able to whittle-down the list to six springs since the others are a straight shape.

So I went around the transport, using the exploded diagram, to find the six springs. I found the Record Lever (11) and E-ring (104) but no spring!

Walla! back in place:

While I was taking apart the transport, I noticed a bend in one of the brackets that lays over the idler wheel. It appeared whoever put these new belts in bent one side of the bar to get the old belts out and to put the new belts in. They didn't want to take the time to take out two more screws to get the job done right $:-\$

I bent the bar back to 90 degrees and put it back in correctly.

I think the owner replaced these belts.

Why do I think that? Well, the loose spring was taped to the inside of the chassis and I was handed a service manual with this gear

He didn't know where it was to go back!

The belts look very good. I just don't think the transport was cleaned before the new belts were put on. I cleaned all pulleys with alcohol to remove the built-up gunk.

Here's where I'm at now. I first tested the tape deck before I took the cover off. If I pressed the rewind button, it would only run for a few seconds and click off. If I pressed the pause button and then the rewind button, the rewind would run all day! I'm hoping that putting the spring back in cures this. I'll clean all of the contacts before the transport is put back in and tested.

I'm not going to do any capacitor or component work unless the transport is functioning properly. On to the cleaning...

Smoky · « **Reply #6 on:** March 19, 2020, 06:13:46 am »

The NAD 6130 cassette deck sounds wonderful!

Here she is being driven by a Kenwood TK-55 receiver from 1968 out of a pair of JBL Control 5 monitors

I can tell the drive motor is getting tired though. This tape deck, without any doubt, has turned many, many miles of ribbon.

Smoky · « **Reply #7 on:** March 19, 2020, 06:36:23 am »

Here are the measurement from the power supply board:

D103 29.3
D107 9.53V
FU102 14.7V

When the motor is in the rewind or fast-forward mode and up against a full-load of tape, you can tell the torque isn't there.

Things get tired as they get old

Maybe there is a replacement motor available?

She's just fine in the "play" mode!

Smoky · « **Reply #8 on:** March 19, 2020, 06:56:44 am »

Wait a minute

Look at the power supply board, could C102 be failing?

I measured pin 8 and I did get 14.7V, but if C102 is less than optimum, could it cause the motor to drag?

I did read about folks flushing the motor and lubricating it with DeoxIT too.

Capacitor test is on the way!

*Well, this is why I didn't just jump in and recap this deck from the start. Rubycon and Nichicon caps are all over it.

And after 35+ years, this 1000uf at 25 is still rock'n:

But a little DeoxIT on the shaft won't hurt

BTW, I read that these little motors have boards in them, and I'm told, that's what goes bad. Has anyone ever cracked one open?

I'd probably do it on a donor motor, but surely not on my only one!

*The oil worked!

I made a batch of a combination of the three DeoxIT products I have. D5, F5, and G5 plus a small drop of clear sewing machine oil. I mixed it. I then put three drops over a few minutes at the spindle with a small water-color brush while the motor was in FF and rewind. I tilted the deck through the process and now the motor flies! No more bogging

The motor must have gotten so dry over the years.

I never put an old capacitor back in either. Here's the new Nichicon UHE installed at C102. I pre-charged it and it measures 1100uf:

She has her cover back on and ready to go back home!

GLouie · « **Reply #9 on:** March 20, 2020, 04:44:25 am »

Good job. Did you do an audio calibration?
The little motors usually have a little board in the rear (under the metal cap) with a speed control circuit. That's what the rear hole with the slit plastic is for, an adjustment pot. The board can go bad, but at this age you are also fighting bearing lube (as you found) and brush/commutator corrosion. Whenever I try to open one of these, I ruin the brushes, so I've given up, which means the back bearing and brushes aren't serviced.

Smoky · « **Reply #10 on:** March 20, 2020, 06:21:07 am »

Thank you GLouie!

I didn't want to take the chance of damaging the motor by fiddling with the trimmer. If I had a second motor, I would've. FloobyDust sent a shot across the bow about this too.

I haven't made a test tape to do the speed adjustment yet either. My repair career is still in its infancy!

The mission was to bring this equipment back to a stable condition and time will tell if more work is needed.

BTW, from what I've read, this motor is used in many other tape decks across many other brands and there is no replacement currently available. One guy was getting into the specs on this motor relating to torque, current draw, range of the speed adjustment, shaft diameter, etc. Nothing on the market comes close.

I'm going to keep an eye out for a spare.

Anyway, I played several tracks from my cassette tape collection and The Talking Heads and Robin Trower have never sounded better

Smoky · « **Reply #11 on:** March 20, 2020, 06:34:29 am »

GLouie, if you have a picture to share of what a board and the guts look like in one of these motors, it would be greatly appreciated

cvanc · « **Reply #12 on:** March 20, 2020, 02:00:15 pm »

Good work! Feels nice to keep the old stuff going, doesn't it?

I can echo other's comments about the speed adjustment on the back of the motor. You MUST insulate the shaft of your screwdriver if you try to adjust this speed control pot. The screwdriver is in contact with the wiper of the pot so there is risk of accidentally shorting to the metal case of the motor and 'oops' you've fried the internal circuit...

GLouie · « **Reply #13 on:** March 20, 2020, 03:28:23 pm »

Sorry, I have no photos of a motor, it's been years since I opened one.

Smoky · « **Reply #14 on:** March 20, 2020, 10:30:35 pm »

Guys, I was able to do a motor alignment today on the NAD cassette deck!

I'll explain how I went about it. Here's my Nakamichi LX-5 and a sealed pair of Radio Shack MPX-90 metal cassette tapes (44-963):

I loaded the the metal tape to the LX-5 and recorded a 3kHz at 500mVrms from the signal generator one channel at a time since I only have one BNC to male RCA cable:

After that, I connected the LX-5 to my beloved Tektronix TDS420 oscilloscope and played the tape

I then took the tape out of the LX-5 and moved the Nakamichi off of the workbench. I brought the NAD 6130 back on the bench and inserted the MPX-90 tape and pressed play. After some tweaking of the motor's trim pot, here's where I left it

I learned so much at this point.

#1, I shut the NAD cassette deck off before I made any adjustment to the motor's trim pot (no chance of a short).

#2, There was no way on God's green Earth that the NAD was going to rival the Nakamichi's Wow and Flutter specs!!! You could literally see the waveform widen and narrow on the NAD reflecting the Wow and Flutter tolerance. The Nakamichi waveform remained almost rock-steady!

#3, I turned the NAD's motor trimmer pot counter-clockwise until I seen the bottom end of the Wow and Flutter "range" break below 3kHZ. I would see 2.9998kHz dance on the screen of the TDS420. I then turned the trimmer pot clockwise until the "bottom" of the range was just above 3kHZ. I figure that if the motor slows slightly over time, it would lower onto 3 kHz.

But that wasn't the best part. The best part was when I brought the cassette deck to my friend's house to install and play it!

I've built custom cabinetry for over 35 years and I outfitted John's entire house about 20 years ago:

...I even mounted a Dual 1228 turntable into the center pull-out drawer!

Fun stuff!

GLouie · « **Reply #15 on:** March 21, 2020, 05:40:04 pm »

Your speed cal is about as good as you can do without a "guaranteed" speed-wow-flutter tape. You have to hope that the Nak is pretty good, which it likely is. Or close enough for cassette.

fanatic1100 · « **Reply #16 on:** May 05, 2020, 05:12:05 am »

Hello participants !!! Please drop off the service manual for the NAD6130 deck on my email - I really need it and will be very respectable. Thanks in advance.
kuleshoff66@mail.ru
kuleshoff66@gmail.com

fanatic1100 · « **Reply #17 on:** May 06, 2020, 07:41:02 am »

Hello !!! If possible, take a photo of the board without the top cover (top view), I need to see the resistors of the variables. Thanks in advance

michalism · « **Reply #18 on:** May 06, 2020, 12:55:19 pm »

A great post! Highly educational for us newbies and I enjoyed the pictures at the end! What a closure

fanatic1100 · « **Reply #19 on:** June 11, 2020, 05:01:41 am »

ЛПМ снят

fanatic1100 · « **Reply #20 on:** June 11, 2020, 05:03:21 am »

idler sizes

fanatic1100 · « **Reply #21 on:** June 11, 2020, 05:03:56 am »

idler sizes

oventech · « **Reply #22 on:** June 22, 2020, 12:54:57 am »

Smoky great work on the NAD deck. bd139 is a great guy from Audiokarma.org. Have bookmarked this thread. And the belt site. Thanks. Bet you made his day when he got the deck back.

oventech · « **Reply #23 on:** June 22, 2020, 12:56:33 am »

Also let us know about those green caps if possible. Thanks.

Smoky · « **Reply #24 on:** June 22, 2020, 02:45:24 am »

Thanks OvenTech!

The green capacitors were left alone. The cassette deck sounded terrific and I felt that there was no need to spend the time pulling and replacing. The tape deck got a lot of TLC, and if and when the time comes, it'll get some more.

I'm just hoping that I got the point across clear enough when it relates to that test tape.

When I recorded the 3kHz test tone on the metal cassette tape and played it back on the Nakamichi, notice how sharp the waveform was measured on the oscilloscope screen.

But when the tape was played in the NAD, notice how the waveform is tight in the middle where the oscilloscope triggers, but at the extremes, notice how the trace tended to look "fatter."

What that is revealing is how stable the tape speed is in the multi-motor Nakamichi transport compared to the single-motor NAD.

Anywho, I'm playing with oscilloscopes now


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Author Topic: NAD 6130 Cassette Deck Repair (Read 6028 times)

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