Japanese Victor RC M70 repair

SpicyLuckster

SpicyLuckster

New Member
Second post on this site, today I put in ten d-cell batteries (which seems like insanity to me) into my Victor RC M70 to finally try it out, but it makes loud obnoxious popping and cracking sounds when anything is even gently adjusted. Power indicator and dial lamps work fine otherwise. I really don't know much about these things but I really want to get it back in functioning order. Any help is appreciated.
 
Superduper

Superduper

Moderator
Staff member
Controls and switches have developed oxidation in the contacts, which is inhibiting good contact, and therefore, there is intermittent connections. You need to clean off the oxidation. This is generally accomplished by flushing the switches and controls with electronics cleaning solvent while working them to scrub off the corrosion. One of the most well known is Deoxit D5 but there are many others which may vary depending upon your location. Generally speaking, you would need to disassemble your boombox to gain access to the controls and switches. This service is the #1 needed maintenance or service required on these old vintage gear. Search the site, there may be many threads about this. Especially the "record bar" is almost surely needing cleaning too.
 
Tinman

Tinman

Member (SA)
Make sure to take lots of pics while you're disassembling it so you can get it back together again.
 
SpicyLuckster

SpicyLuckster

New Member
One more thing, while I'm waiting for my local electronics store to get a shipment of Deoxit in, I thought I'd tackle getting the power situation sorted in the meantime. Since it's a Japanese model, this means it's designed to run off 100v grid, and I'm in the US, where our grid is based on 120v. This Japanese model also lacks a voltage selector usually found on the side of the other M70's from other regions. Now keeping in mind I'm not very well versed in electric power supply/load etc which is why I'm reaching out to you more knowledgeable folk. I know that by plugging the thing into the outlets would fry it internally. I've been looking on Amazon and came across a seemingly applicable stepdown converter I could use, linked below, but the only thing holding me back from going ahead and buying it is the fact I don't have the original power cable to plug into the boombox AC port. I'm having issues finding a cable online, so I'm hoping someone here can point me in the right direction. Thanks.

 
SpicyLuckster

SpicyLuckster

New Member
I think I might've solved my cable and voltage problem, I found the cable and a transformer auction on eBay for mega low-ballz, but the wart option is tempting, those are the little plug-ins with the built-in low-wattage stepdown with a simple output on the other side, right?
caution said:
How about a DC 'wall wart' adapter? It might be cheaper than a step-down transformer.
Click to expand...
 
SpicyLuckster

SpicyLuckster

New Member
caution said:
Exactly! They use a barrel plug.
Click to expand...
I read through this older forum pertaining to powering the M70, a lot of useful information there.

www.boomboxery.com

RC-M70 12VDC jack

anyone know any specs on the 12VDC barrel jack? what size it is? (my guess it accepts 3.0mm ID, 6.5mm OD Plug) voltage tolerance +/- from 12V? current needed? i'm guessing around 5 amps. wonder if this will work? http://www.digikey.ca/product-detail/en/CA-2224/CP-2224-ND/1682081
www.boomboxery.com www.boomboxery.com

This would mean using either a 12v AD to DC wall wart adapter OR a step-down to 100v through AC-in should work for the use case.
 
A

aiwapanasonic

Member (SA)
I am powering a Victor m70 with a15v 5amp or 6 amp Toshiba laptop adapter. You could try a generic one but these Toshiba chargers are the best quality. The jack is a perfect fit for m70 and if you get a Victor m90 too. This Victor jack is hard to find in generic adapters but the Toshiba laptops used it.

Beware of the reverse polarity! On the Victor, center is minus. You need to either reverse the plus/minus by cutting the cord or better, opening up the adapter and desoldering the wires; then flip them and solder again. I just did this last week on two adapters.

I have also been using a Panasonic RX DT8 this way by connecting to the plus and minus terminals in the battery box as it does not have a jack.

The Victor m70 DC voltage is 15v, not 12; probably anything between 12 to 15 will do. But the box clearly has 15v written plus the Toshiba charger is a perfect 15v DC.

If you look for a AC converter, I read somewhere that a Nissyo industry one is good and I got one and it is. I also got another brand but it outputs 110v rather than 100v. This is in Europe and i wonder if it’s due to the mains voltage being closer to 240v than 220v; in any case, the DC Toshiba charger takes care of all this.

I always measure to be sure. Also, if using DC, it’s worth disconnecting the AC supply inside the box if you are worried about forgetting and plugging it into the mains.

One more suggestion - there is a YouTube video of a Japanese guy doing the restoration end to end including sliders… worth watching; it’s 1.5 hours.
 
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A

aiwapanasonic

Member (SA)
Just re-read the other trail; I learned from it when doing my Panasonic mod. The bigger Toshiba charger is rated at 15v6amp or 90 watts. This is more than enough for a m70 or m90. The 5amp one is enough too. I have measured the output: it is a stable 15.35v; they have thick cables; fuse; shielding; there is no FM interference. They sell for 10 pounds on the UK ebay.

P.S. you can find a thread here on this forum about the different JVC m90 versions where a user says they plug a Japanese m70 in the US mains for extended periods with no problem. Maybe you can. But I fried a Japanese Sanyo this way with my shoddy second AC converter only with 10v over on AC power so why risk it.
 
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SpicyLuckster

SpicyLuckster

New Member
aiwapanasonic said:
I am powering a Victor m70 with a15v 5amp or 6 amp Toshiba laptop adapter. You could try a generic one but these Toshiba chargers are the best quality. The jack is a perfect fit for m70 and if you get a Victor m90 too. This Victor jack is hard to find in generic adapters but the Toshiba laptops used it.

Beware of the reverse polarity! On the Victor, center is minus. You need to either reverse the plus/minus by cutting the cord or better, opening up the adapter and desoldering the wires; then flip them and solder again. I just did this last week on two adapters.

I have also been using a Panasonic RX DT8 this way by connecting to the plus and minus terminals in the battery box as it does not have a jack.

The Victor m70 DC voltage is 15v, not 12; probably anything between 12 to 15 will do. But the box clearly has 15v written plus the Toshiba charger is a perfect 15v DC.

If you look for a AC converter, I read somewhere that a Nissyo industry one is good and I got one and it is. I also got another brand but it outputs 110v rather than 100v. This is in Europe and i wonder if it’s due to the mains voltage being closer to 240v than 220v; in any case, the DC Toshiba charger takes care of all this.

I always measure to be sure. Also, if using DC, it’s worth disconnecting the AC supply inside the box if you are worried about forgetting and plugging it into the mains.

One more suggestion - there is a YouTube video of a Japanese guy doing the restoration end to end including sliders… worth watching; it’s 1.5 hours.
Click to expand...
I really appreciate this advice, I think I might just settle for the AC route because I found a used Nisso stepdown like you mentioned for super cheap, but this is definitely useful and I might end up getting one of those Toshiba laptop chargers you mentioned just for the sake of making portability less of a hassle. Thanks for the supreme help!
 
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Superduper

Superduper

Moderator
Staff member
The case for just retrofitting it properly is that someday years later, you might forget and plug it directly into AC without the adapter, or someone else might do it. Swapping out the internal transformer just fixes it permanently and you no longer have to worry about wrong voltage, and you don't have an extra accessory keep track of, or lug around with you if you're taking it somewhere else with the intention of plugging it in (to a party, for example).
 
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A

aiwapanasonic

Member (SA)
I am a almost total rookie and don’t know enough about electric circuits to do the retrofit. Unless I can find a donor that is plug and play. So I am stuck with the extra adapter, which on one box I just zip tied to the back. Or the AC converter. But for safety (in Europe you are guaranteed to fry something if you plug a 100v machine to the mains) you can unplug the fuse and the power socket inside. Or put electric tape over the AC plug…

Or send it over to one of the masters to do it for you :)
 
SpicyLuckster

SpicyLuckster

New Member
aiwapanasonic said:
The hardest thing on this specific box is convert the FM to full range. If anyone knows a mod, I would be jumping on it.
Click to expand...
An easy alternative to modifying the box itself would be to just find a good am/fm stereo tuner and then plug it into the line-in of the box.
Regarding the retrofit I am almost in the same boat as you, I need to learn how to solder but otherwise I'd be willing to make the transformer swap.
 
SpicyLuckster

SpicyLuckster

New Member
I still appreciate the idea, Super, but I just really lack the tools and skills for swapping the transformer right now haha... :lol:
 
SpicyLuckster

SpicyLuckster

New Member
FInally got the chance to open her up, I've removed the back cover (mostly, but the antenna wires seem to be stuck onto the back casing so i'll just cut the ext. antenna connector solder points) and everything to this point seems fine except for some leakage on the secondary board here1731368763033.png
(i apologize for my lack of knowledge with each board and the functions they serve) Assuming this is the radio board, I'm hoping this leakage isn't going to get in the way of any of the line-in functions. I know how recommended it is to replace the leaky capacitors and clean the board but I lack the equipment for that. Other than that, most of the other components look clean so I'll continue with the disassembly.
 

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