M90 Restored Thanks to y'all on Boomboxery :-) JT & Chronic

[Transistorized]

So I finally had a chance to get caught up on this progress after the long weekend. I'm sitting in an instructor-led corporate training class right now, bored out of my skull (but on a break)...

Really glad you got the box back and the parts unit you were lucky enough to pick up from Chronic had everything you needed to get it to 100%!

Now, all you've got to do is blast it as loud & proud as I did! Somehow, I don't think that's going to be a problem!

Thanks for being trusting and doing this deal with me. I'm super happy it stayed in the Boomboxery family!!!!

Thanks JT. You're right about getting lucky. Its as if Chronic had a vision that someone out there right now has a M90 at the shop in need of a donor part.

Chronic said the parts were known to be good. He couldn't have been more honest about this as all the parts were verified to be operational (aside from cassette deck which was noted at time of sale). The reason I say this is because I found out that the tech simply took the whole Amp board from the donor Chronic sold me and swapped it out in place of the original. No soldering needed. Just plug and play. No issues at all. Playing right now as a matter of fact

In a world full of folks trying to get one over on someone I have yet to find anyone like that on here. If anything, everyone has been more than honest about what they have sold me. Everyone watches out for one another and I like that. I will be sure to show that same respect for you all if and when I decide to sell anything.

This is great news! So many M90's saved lately, it is nice to see.

Just great!

Thanks Guys

What a great success story. I'm restoring my M90 at the moment, this was some good inspiration to get back on it. The volume pot is replaceable, but it might have to be a ganged setup to retain full original functionality. By the way, you asked for feedback at the end of your video. I thought it did a good job capturing the spirit of this hobby well. Your excitement is tangible!

Congrats bro!

Hi Caution. The whole time my machine was in service I found the key word to bring up the Volume pot on Google. I first did a Image search and found that typing 6+1 Potentiometer brought up a few good images. Traced those back to the website and whalla! A bunch of potential for the correct Volume pots showed up.

Heres the link directly to the best website I found to have the correct "looking" pot

http://www.bestronusa.com/category/index.cfm?cid=81&lvl=2

Also unlike other potentiometers I found that the M90 Volume pot it is a Linear (B) not Audio taper (A). That explains why the volume needs to be turned up to a higher number unlike the Conion C-100F which uses An audio taper.

Also, as you may know its a 50K Ohm. They have those in a 6+1 configuration. It is unclear as to whether the D shaft will relocate the knob or if the +1 pin for the Loudness is correctly mapped within the circuitry of the potentiometer.

My tech was in the middle of ordering several pots (not knowing if they would allow 100% functionality - balance / loudness switch) when Chronic came along with the required original parts. So we ditched the unknown and went for the donor box.

Good luck to you on your search though.

 

[caution]

I can't believe my luck.
A couple of years ago I tore apart a Panasonic RX-DT670, since nobody here wanted it for the price of shipping. Turns out it's got the same volume pot as the M90!

But, as you can see, the shaft is a little longer. It's not Alps though, it's Matsushiata, but I had to search for it using Panasonic's number.

What's the number though? Encompass had a full list of parts. After comparing the "Panasonic control" entries, I found that the DT670 uses a EWCTNAF25B54, which translates to an EWCTNA style pot with a (F)lat 25mm shaft with a B-style (midpoint) tap and 50000 ohms. I confirmed this one using a Panasonic potentiometer spec document.

I wanted to see if even more models had this pot, so I downloaded the a copy of the DT680 service manual. Bingo, same resistance, same loudness tap. But, the DT680 has a motorized volume, so unfortunately the physical style is different, it lays flat on the board with the shaft sticking vertical. In any case, a 670 is worth the sacrifice, not sure about a 680!

So, since this pot comes from a much newer model, I would think the chances of finding the part still in stock somewhere, or a used model on the cheap, might be an alternative to an RX-5050.

It would be the best choice, but if one must, fixing the pots is not that bad as long as there isn't any damage to the wipers or tracks.

By the way, the seventh pin hanging out by itself from the other six is not actually a loudness tap. It's another pin on the pot structure. The loudness taps are in the main row of pins. It's sort of jumbled, but there are two loudness taps, two wiper pins, and three pins for the two resistors (one end is a shared pin for ground).

I'm also going to test some RK27 Alps pots which have the same requirements, but are physically smaller and would have to be mounted into the original bracket.

 

[Fatdog]

Dang, that is great news, Eric!!

Look for the price of RX-DT670 boomboxes to skyrocket.

 

[Transistorized]

That's excellent news caution. That 50K Ohm B series is it. Most are audio taper versus linear. The panasonic boxes seem to be the ones with the most compatible pots

 

[Fatdog]

You might be able to buy the pot without having to buy an entire RX-DT670

http://www.mcmelectronics.com/product/P-EWCTNAF25B54

 

[caution]

Hah, I saw that this morning and ordered a few, we'll see if I get them!

 

[Transistorized]

Reviving this thread caused me to have to pull out my M90 again. Sweet! Video upload in Collections section. She's alive and well. I might get a pot to restore my parts chassis if this works for you Caution

 

[caution]

More models available and not impossible to find on the cheap if necessary.
The original M90 bracket must be re-used.
The EWCTNA pots have bracket pins positioned too far back, but could maybe be modified to work in a pinch.
I opened an M90 pot and found no fingers. The wipers were similar to the Panasonics, which look like dented rings. Perhaps it's more robust?

RX-DT401: EWCT5AF20B54
RX-DT600: EWCT5AF15B54
RX-DT610: EWCT5AF20B54
RX-DT630: EWCT5AF20B54
RX-DT640: EWCT5AF15B54
RX-DT670: EWCTNAF25B54
RX-DT680: EWCT5AF20B54
RX-DT690: EWCT5AF20B54
GX90CD: EWCT5AF20B54
RXCS750: EWCT5AF20B54
RXCT980: EWCT5AF20B54
RXDS101: EWCT5AF20B54
RXDS102: EWCT5AF20B54
RXDS202: EWCT5AF20B54
RXDS620: EWCT5AF20B54

EWCT5AF20B54 and EWCT5AF15B54:
Pins 1-6 must be straightened and pin 7 must be jumpered.

EWCT5AF20B54:
Correct shaft length.

EWCT5AF15B54:
Shaft is short by 5mm. It's ABS, so it could be welded/lengthened in a pinch.

EWCTNAF25B54:
Shaft must be shortened by 5mm.

They still make "B50K" pots in China, and I've ordered a few to try out, but they would be more work to make fit.

 

[Transistorized]

My eyes are peeled to this post. I am very interested in the outcome of this. The M90 is worth the effort you are putting into this. God bless you

 

[Newclairtone7980]

I can't believe my luck.
A couple of years ago I tore apart a Panasonic RX-DT670, since nobody here wanted it for the price of shipping. Turns out it's got the same volume pot as the M90!

But, as you can see, the shaft is a little longer. It's not Alps though, it's Matsushiata, but I had to search for it using Panasonic's number.

What's the number though? Encompass had a full list of parts. After comparing the "Panasonic control" entries, I found that the DT670 uses a EWCTNAF25B54, which translates to an EWCTNA style pot with a (F)lat 25mm shaft with a B-style (midpoint) tap and 50000 ohms. I confirmed this one using a Panasonic potentiometer spec document.

I wanted to see if even more models had this pot, so I downloaded the a copy of the DT680 service manual. Bingo, same resistance, same loudness tap. But, the DT680 has a motorized volume, so unfortunately the physical style is different, it lays flat on the board with the shaft sticking vertical. In any case, a 670 is worth the sacrifice, not sure about a 680!

So, since this pot comes from a much newer model, I would think the chances of finding the part still in stock somewhere, or a used model on the cheap, might be an alternative to an RX-5050.

It would be the best choice, but if one must, fixing the pots is not that bad as long as there isn't any damage to the wipers or tracks.

By the way, the seventh pin hanging out by itself from the other six is not actually a loudness tap. It's another pin on the pot structure. The loudness taps are in the main row of pins. It's sort of jumbled, but there are two loudness taps, two wiper pins, and three pins for the two resistors (one end is a shared pin for ground).

I'm also going to test some RK27 Alps pots which have the same requirements, but are physically smaller and would have to be mounted into the original bracket.

thanks don't like glueing things id like to get P-EWCTNAF25B54. pot like you said was the same if you know anybody who sells them let me know thanks

 

[Transistorized]

This post coming back to the surface takes me back to that day when my M90 came home fully repaired. Still enjoying and treasuring it.

Also, I continue to be very thankful to JT and Chronic. JT for the machine and Chronic to the rescue with a chassis.

This machine continues to be Loved almost daily. It has never sat for more than a couple days without being powered up and used. On occasion I still pinch myself for being a proud owner

[sharedmedia=core:attachments:37342]

 

[Newclairtone7980]

This post coming back to the surface takes me back to that day when my M90 came home fully repaired. Still enjoying and treasuring it.

Also, I continue to be very thankful to JT and Chronic. JT for the machine and Chronic to the rescue with a chassis.

This machine continues to be Loved almost daily. It has never sat for more than a couple days without being powered up and used. On occasion I still pinch myself for being a proud owner

looks nice still trying to find a volume pot for my m-90

 

[bklyn sound]

Looks great congratulations

 

[Transistorized]

This post coming back to the surface takes me back to that day when my M90 came home fully repaired. Still enjoying and treasuring it.

Also, I continue to be very thankful to JT and Chronic. JT for the machine and Chronic to the rescue with a chassis.

This machine continues to be Loved almost daily. It has never sat for more than a couple days without being powered up and used. On occasion I still pinch myself for being a proud owner

looks nice still trying to find a volume pot for my m-90

It was a nail biter for me in my quest to land a M90 volume pot. While my box was sitting in pieces I got lucky with snatching up Chronics OE chassis parts. On a good note it seems as though there has been great progress made on trying to locate various other part numbers and boombox models whose pots will work with the m90's on this forum. In a pinch I know the Panasonic RX-5050 will work with some degree of issue in regard to balance control and loudness. I know what you are going through and I feel your pain

 

[BoomboxLover48]

I can't believe my luck.
A couple of years ago I tore apart a Panasonic RX-DT670, since nobody here wanted it for the price of shipping. Turns out it's got the same volume pot as the M90!

But, as you can see, the shaft is a little longer. It's not Alps though, it's Matsushiata, but I had to search for it using Panasonic's number.

What's the number though? Encompass had a full list of parts. After comparing the "Panasonic control" entries, I found that the DT670 uses a EWCTNAF25B54, which translates to an EWCTNA style pot with a (F)lat 25mm shaft with a B-style (midpoint) tap and 50000 ohms. I confirmed this one using a Panasonic potentiometer spec document.

I wanted to see if even more models had this pot, so I downloaded the a copy of the DT680 service manual. Bingo, same resistance, same loudness tap. But, the DT680 has a motorized volume, so unfortunately the physical style is different, it lays flat on the board with the shaft sticking vertical. In any case, a 670 is worth the sacrifice, not sure about a 680!

So, since this pot comes from a much newer model, I would think the chances of finding the part still in stock somewhere, or a used model on the cheap, might be an alternative to an RX-5050.

It would be the best choice, but if one must, fixing the pots is not that bad as long as there isn't any damage to the wipers or tracks.

By the way, the seventh pin hanging out by itself from the other six is not actually a loudness tap. It's another pin on the pot structure. The loudness taps are in the main row of pins. It's sort of jumbled, but there are two loudness taps, two wiper pins, and three pins for the two resistors (one end is a shared pin for ground).

I'm also going to test some RK27 Alps pots which have the same requirements, but are physically smaller and would have to be mounted into the original bracket.

Eric the Magician does it again! Great information!