JVC m90 vs Victor m90

[aiwapanasonic]

I didn’t mean to cause any contention; just stating what we observed because I was in strong disbelief as well. We= three people, one of whom is the restorer, as experienced with boomboxes as some of you guys, across all boxes from the 70s and 80s. Also another collector with sensitive ears. We even did a quick battle with Panasonic 5350 (I listened to this) but it was very quick because the Panasonic was just on a different level, as nice as it is. We also compared against an Aiwa CS880 and the Aiwa stood up really well.

Anyway, just to say these are practical tests on machines that came in not working conditions and had the mechanics restored and cleaning of switches snd pots.. At the end, they worked equally well and sounded identically (all 4 Victors on the one hand and the reference JVC on the other).

No recapping, all original (why recap if it’s working great?) By the way if recapping is done, then it should be done with the same type of new caps because I have read that the choice of caps and chemistry inside will influence the sound. And again, why recap unless a model is known to have leaky or deteriorated caps? From what I have read, caps aren’t an issue for this model.

We didn’t swap the speakers, that would be a nice experiment but it would only explain the why. Ideally we need the Victor schematics but it’s nowhere to be found.

If anyone is keen to repeat the test, definitely you should keep the power supply as a constant. I have seen people plugging the Victors or Canadian JVCs in the US mains, which sounds wrong.

One more observation: the DC power supply for m90s is different. Some have 15v written on the back and some 12v. This is also stated on the service manuals for the export versions. The difference is there between export versions. The Victor has 15v. This puzzles me because they all take 10 batteries. Cars around the world run on the same voltage too. There is a US box with 61w has 12v and multi-AC voltage. Then the Canadian m90 has 70w written and 12v DC. I attribute this to the convention in the counties but it makes me wonder what DC adapter is safest to use.

Final food for thought: the top JVC deck TD V 1010 is the export version of Victor TDV 721. You’d think they are the same but apparently they are not, based on Tapeheads, the domestic version is slightly better. Just goes to say there are other examples like this even by the Victor company.

 

[aiwapanasonic]

I managed to get a copy of two recordings; they compare the JVC 70w vs two different Victors. Feel free to listen, with good headphones because already the video is compressed and what you hear on the recording is about 50% of what you hear live. If you listen over bluetooth, you won't hear the difference.

Any difference is marginal. Again, I am very careful to say one is not better than the other; just that there is a slight difference. I read today that PC 55 and PC 550 have a different sound profile, maybe due to different speakers. Anyway let's listen and have fun.

they are mp4s; best to download to your PC because they otherwise get compressed once more like a youtube video:

JVC m90 vs Victor m90

 

[Superduper]

Nah, I don’t care about tests like this on 50 year old gear. You work on these things long enough, you know that age has an effect.

 

[aiwapanasonic]

@Superduper,

@Reli

Is there a checklist of common issues or points to restore in a m90 so it sounds well? I have read in this forum and another site, by Reli I think, about:

• Speakers tearing
• Deck: a fusible resistor
• Deck: a plastic wheel with reflective surfaces
• Switches mainly cleaning but no failures
• Potentiometers failure. Especially the one for the volume - this one seems to be the hardest to fix; maybe impossible to fix, when the conductive lines are scratched; there is no known replacement pot from another model; is it still true?
• Recapping – you mentioned this; is it really needed? Are there some caps that are more critical than others? For example, on some Nakamichi decks there are yellow caps that need to be fully replaced. On other decks, only the power supply caps are a problem or a leaky cap on the motor board.

What about calibration with test tapes, is this normally needed?

What about heads, can you take one from a donor deck from the same age like a two-head JVC kd a7?

And is there such a thing as “sound tuning” ? I have heard about this on one youtube channel where the restorer apparently improves the imperfections on the signal path; or tweaks the equaliser; but I don’t know if he does it on the m90.

 

[Reli]

You can read the M90 article on Wikiboombox, I didn't write it so I can't comment about known failures. But as far as caps go, if someone wants to just replace a few caps and see if it improves anything, I would recommend doing the power supply caps and the ones between the woofers and tweeters. But I wouldn't recommend replacing any of the others without replacing all of them.

 

[RoZyBoom]

First, @floyd I'm going to say that 100V means nothing. All the best boomboxes were made by Japanese companies, and it is my experience that they would not make them lesser for their own market than for export. Also, plenty of pieces of hardware that deliver exactly same specifications in the 100V Japanese trim vs. American - for example. So the takes power to make power argument I don't think holds.

Second, I've seen that for example the JVC PC-55 and PC-550 speakers differ - have you confirmed same PN references on the woofers in both units?

Finally, the RC-M90 has speaker outputs - why not switch the switch and measure the power being output right there with a meter? I know this isn't a test of actual sound nor quality sound nor distortion - all very important points, after all, what good is power if it is unusable...but as a starting point, a measurement of the amplifier power output is going to be quite telling.

P.S. I'm reading that 10w output is 40dBm and at 100w it is 50dBm, so how many dBm can be between 20w and 25w?

 

[floyd]

First, @floyd I'm going to say that 100V means nothing. All the best boomboxes were made by Japanese companies, and it is my experience that they would not make them lesser for their own market than for export. Also, plenty of pieces of hardware that deliver exactly same specifications in the 100V Japanese trim vs. American - for example. So the takes power to make power argument I don't think holds.

Second, I've seen that for example the JVC PC-55 and PC-550 speakers differ - have you confirmed same PN references on the woofers in both units?

Finally, the RC-M90 has speaker outputs - why not switch the switch and measure the power being output right there with a meter? I know this isn't a test of actual sound nor quality sound nor distortion - all very important points, after all, what good is power if it is unusable...but as a starting point, a measurement of the amplifier power output is going to be quite telling.

P.S. I'm reading that 10w output is 40dBm and at 100w it is 50dBm, so how many dBm can be between 20w and 25w?

My question is have you confirmed anything that you think you know ?.
Where's the proof . show me the data sheets on every unit you mentioned and every speaker . those would tell you the specs .
Maybe I didn't know wtf I was talking about at the time so why don't you just show me how wrong I am .its easy all you need are solid facts.

 

[RoZyBoom]

@floyd, not wanting to get into an argument, or get into a whole voltage, amperage, wattage thing...

But out of curtesy for your data sheet request, here is a high power Technics SE-A100 amplifier.
Japan Spec: (Note: 400W power consumption rating at 100V)

Technics SE-A100の仕様 テクニクス

audio-heritage.jp

Euro/North American Spec (Note: 770W power consumption rating at 120V)

https://www.hifiengine.com/manual_library/technics/se-a100.shtml

The different voltage version carry different transformers (I've seen them inside) but they are all spac'ed the same to accepted standards and deliver same rated output power to speaker outputs. I have also seen a multi voltage version spec somewhere, and it also was rated the same.

However, considering these are boomboxes, and they are not crazy high-powered or risky to measure, as suggested in my "Finally" point, measuring the Victor and JVC version output power with a meter would be a clear, easy, and risk-free.

Although it should be kept in mind that the Victor 100V version should have a sufficient amperage and quality step down unit, as some low-cost/low-quality step-downs aren't good for the job and could skew results. For example, I've seen some that aren't really for electronics like audio because of some type of circuitry in them, and they produced noise on audio or rendered CD players (not applicable here obviously) unusable. I've had to buy a rather heavy big one with a large transformer for certain piece. (Edited - added watt ratings from spec sheet in case people don't have HiFiEngine access to view.)

 

[aiwapanasonic]

Having reviewed the available service and user manuals and brochures (JW/W; C; the main one that is missing is the L for the European version), the 61w vs 70w difference between different global versions seem to be indeed just some convention. The parts and output power look identical on the Service Manual between the JW and W versions: what is published is 40w (20+20). Between these two models, there is only a minor difference in three electrical components on the FM tuner, but I don't think they matter; the main difference is in the power board and the AC to DC transformers; this is on the service manual.

On the Japanese brochures for the Victor, the specs are identical with the global versions except for the output power: it is published as 30w (15+15) for DC / EAIJ. Not sure if this is another difference in convention. There is a similar difference between the global m70 and the JDM one: the JDM m70 is published at 20w EAIJ /DC while the global one is 30w. Is this about testing on batteries vs AC power? If the AC transformer outputs 18v DC and batteries output 15v DC, that’s a 20% difference.

When it comes to the different inputs and outputs, both the Global and Japanese versions of the m90 are rated the same - Line in, Line out and external speakers supported. The weight is different but there are some hardware differences like the lack of SW, lack of FM fine tuning and some others; obviously the power transformer.

Finally, I found different part numbers for the woofers but no specs:
JVC HSA2005-01G -> there is a photo on this forum, it has 20W written on it
JVC HSA2005-01J -> there is a photo on this forum, it has 25W written on it
JVC HSA2005-01BCS -> have not found any photos

Woofer parts are here on an old catalogue:

https://www.pacparts.com/parts/list.cfm/MFG/jvc/row/256001

https://www.ued.net/ued/searchResults.jsp

There aren't different PNs for the tweeters.

This is the Japanese Victor m90 specs from a catalogue, on the left side.

I also thought about testing the output to the line out or ext speakers but again this won’t help prove much as you could still explain differences with the state of the machines after 40+ years.

Really what is needed is the Japanese Service Manual to confirm any differences on the signal path like filters that change the sound profile. Or otherwise, a close comparison of the signal path on the boards and the speakers.

 

[Superduper]

These M90 spec rating differences from different geographic versions have been debated ad naseum countless times before. They are TOTALLY meaningless, if you are comparing specs to determine which is better because each spec and rating published is intended specifically for the country for which that model suffix was released. They were never intended and probably doesn't even use the same testing criteria rating from country to country. So if you take a USA spec and compare against a Japanese or European spec, it means absolutely nothing because the Japanese or European models were never rated using the USA rating system, and vice versa. One country might rate power output with a single channel operating a time, another might use both channels operating together, and then you don't know if the spec is measured at the posted power output rating watts/THD or if it was done using max volume on control regardless of distortion. Perhaps power consumption on one is based upon rated output and another is based on volume control at max, once again, regardless of distortion. Bottom line is that they all use the exact same amplifiers, etc. so they are all capable of outputting the same or very similar power subject only to circuitry differences (such as DIN vs RCA type circuitry). Also ranking them based on the 4 or 5 marking on a volume control is never a way to test output power. You need to use lab equipment and inject a stable equal signal, with the amplifier at max output, and increase the input signal amplitude until the output just reaches clipping, or distortion is measured at a specific level (for example, 1% THD or 10%THD). The power level will then be the spec, with the limiting factor always being the amount of power output at a specific THD level. The volume control level position is irrelevant because you are presuming that these pots have a perfectly equal curve and carbon track wear level and they frequently do not. Simply listening to one or another at a predetermined knob position and deciding which model is "better" is useless. Many boomboxes will max out (distortion wise) far before the volume control is at max and the level where distortion is equal is really the way. If you feel one suffix version is better, then that is fine, it's better for you. But insofar as making a conclusion that one is better than another is.... well, let's just say I've said all I want to say on this subject and I am un-watching this thread any longer.

 

[Reli]

Yes, the Japanese EAIJ/DC standard is indeed measured when using batteries. But most boomboxes make more power when using AC, because the transformer usually provides more voltage than the batteries do.

Other countries use other measurement standards, some of which are total BS like MPO "Music Power Output".

The most useful standard is "FTC" or "RMS Minimum", which indicates the minimum amount of power it makes across a broad frequency range. And "RMS Max" would be the maximum it makes across that same range.

 

[RoZyBoom]

I honestly cannot believe no one has measured these RC-M90s at the speaker output yet, considering their standing.

 

[aiwapanasonic]

I am tired of this and unless the Victor company are kind enough to respond to my request and send me the Victor service manual, will leave it. Indeed this difference has been discussed extensively.

Better questions are about the [has one been found yet?] replacement or repair of the m90 volume pot; or how to fix the screen on the PC 55s

JVC PC-55 PC-550 Display ribbon problem - anyone find a good fix?

This is the Z axis tape people were talking about https://www.adafruit.com/product/1656 Both Apple and Sharp have used it (or something similar) in their products. No I haven't tried it for an LCD repair. This looks incredibly promising, because it is able to double side, glue multiple points...

www.boomboxery.com

 

[floyd]

I honestly cannot believe no one has measured these RC-M90s at the speaker output yet, considering their standing.

Maybe they have but haven't chimed in yet . I mean not everyone who test the m90 post up here.

 

[RoZyBoom]

Maybe they have but haven't chimed in yet . I mean not everyone who test the m90 post up here.

Someone is sitting on a 250K+ view video out there. Get on it..."someone" with these units and a meter.

Better questions are about the [has one been found yet?] replacement or repair of the m90 volume pot; or how to fix the screen on the PC 55s

oh man...the PC-55 screen...and now you tell me M90 has a "fatal" issue on the volume pot? DAMN! At least the PC-55 can be used with a bum display but no volume control? When I look at a broken PC-55 deck display during playback I imagine it is displaying tears of sadness, sadness, sadness.

By the way aiwapanasonic, I don't think the PC-55 display can be fixed. I'm no brain surgeon, but I gave it an honest go, and it's NO-GO.

JVC PC-55 PC-550 LCD display - I'm declaring it irreparable

If you've lost segments of your JVC PC-55 / PC-550 LCD display, and unless something basic and obvious like edge of the ribbon where a single connection point was lost and you can restore contact with a small piece of adhesive/tape, I'm declaring the JVC PC-55 LCD display currently irreparable...

www.boomboxery.com

 

[Superduper]

I honestly cannot believe no one has measured these RC-M90s at the speaker output yet, considering their standing.

Why? ALL M90 versions use the exact same amplifier output chip.

JVC PC-55 PC-550 Display ribbon problem - anyone find a good fix?

This is the Z axis tape people were talking about https://www.adafruit.com/product/1656 Both Apple and Sharp have used it (or something similar) in their products. No I haven't tried it for an LCD repair. This looks incredibly promising, because it is able to double side, glue multiple points...

www.boomboxery.com

 

[RoZyBoom]

Why? ALL M90 versions use the exact same amplifier output chip.

Well, it seems that people are finding various levels of power, so measurement at output would settle this once and for all.

What is interesting to point out is that many boomboxes, JVCs included, list maximum power output at 10% THD...this is a lot of THD.

Regarding your video...thank you.

FPC - Flexible Printed Circuit - at least now we know what we're dealing with inside this PC-55 display.

Heat. May have to try that solution. "If you have nothing to lose..." . It's simple enough to be quite honest. Much more simple than any solution anyone has thought of so far. I hope these 40 year old FPCs can handle the heat cycle, but if we're doing it - they need it. Seems like 175C perhaps based on that video? Or 150C? What do you guys think? DAMN...if that will work...that will be an AMAZING solution. Cover with some foil, run an iron over it and DISCO! I hope it is that simple. I hope I retract that unfixable claim. At this point I don't have a display issue deck on hand, but one will land here soon enough. If someone has a PC-55 faulty display deck and wants to try this heat cycle solution - please document and share process and results.

In the video regarding FPC he says...
"I have to say that it's a lot more challenging than first case but it's still possible if you know what you're doing."

It seems that any replacement application would have to be done with heat, and I'm not sure everyone would have the result desired. Also, I seem to recall that in one case where I removed the FPC off that step-edge of the LCD glass display, the connection point came off with it and left the glass with nothing - little tiny visible sliver at the layers meeting. There would be nothing to attach a new FPC to, so we need to keep the FPCs that are in there already, just get the connection back somehow. I still have that PC-55 display glass from which I removed both sides of the ribbons. When I find it at some point, I'll take a picture of it and post it here for informative purposes. Therefore, this heat cycle solution reusing the ribbon that is there already would be the perfect solution. Fingers crossed! I'll try it first chance I get, unless someone beats me to it.

 

[aiwapanasonic]

You can try heating the residue on the glass to see if it melts at all; who knows what type of glue they used. Has this method been tested on PC 55 at all?
It may be worth starting a new thread for this PC 55 display fix as the old one is closed, and this one is for m90

 

[RoZyBoom]

Why? ALL M90 versions use the exact same amplifier output chip.

You can try heating the residue on the glass to see if it melts at all; who knows what type of glue they used. Has this method been tested on PC 55 at all?
It may be worth starting a new thread for this PC 55 display fix as the old one is closed, and this one is for m90

I added the video the the "irreparable" post, but a new post will be needed so that it comes up in searches. Indeed, I can't wait to make that "irreparable" post "irrelevant" and deleted. I SO hope this heat cycle method works - it would be SO SIMPLE! I'd try it now, but I don't have a candidate deck for this - I destroyed mine testing the axis tape and conductive paint. Someone...the sooner, the better if you have a busted display deck. Also, it's not high risk. I feel a bit dumb not thinking this up before the axis tape and conductive tape. Talk about the simple solution being too close to the face to be seen!

For those of us who absolutely adore the PC-55 and rank it as favourite, this display fix working news would be incredibly amazing boombox news.

 

[Transistorized]

I can appreciate the work that went into this study. As others have mentioned, the history of the radio, how it was/is stored, the history of how it was used, will affect the outcome of performance.

I know the radios sold in different areas throughout the world include different wattages on the case, but this is more to do with the varying grid voltages around the world, and how that usage is therfore calculated in retrospect to the power consumption of the radio. It in no way translates to the "efficient" output power of the amp chip in the radio.

Now, there are situations where you can force an amp chip to perform higher than was intended in total output power. One way, is to over-volt the circuitry. For example. I have a JVC RC-M70W model that is a 110V unit. I did find that powering it up with 120V line voltage does supply the amp chip with more voltage allowing it to belt out more "noise" but didn't actually increase it's performance. If you were simply trying to go a decibel louder, you could technically do that but increasing the voltage isn't the best on the radio and undoubtedly will shorten its life. These radios have unregulated power supplies, so any voltage variables, while stepped down to a lower value of percentage by the transformer, are passed along through the transformer to the radios circuitry. So, with a 10V AC mains variance, the transformer might only pass 1 to 2V more DC to the circuitry.

In my opinion, all M90s (when new) performed on par with each other. The reason I say this, is because they all used the same amp chips and ohm speakers. Powering them by a regulated DC power supply with the same output power through the DC jack would give you the best possible example however, all components are well seasoned and of unknown history, so even two different radios amp chips won't necessarily all be on par with another along with varying resistor and capacitor values to only add to the varying output results.

Finally, in addition to my W model, I have 2 other JVC M70JW of same specs. One sounds better than the other with deeper bass. So, the only thing I have learned is that every radio is slightly different and that age and usage only exaggerated that finding. Heck, even my ears hear things differently than they used to. I guess my specs have changed over the years also Most of my values have gone down..haha.

Interesting read for sure.