JVC 3090 Hack lost in time...

[Obiw4n]

Hi, If you check the images below I'll explain...

Inside my newly acquired JVC 3090EN I found an after market modification which I think is an AM radio hack or possibly a TV mod, you see my CRT on the box is borked at the moment and I wanted to see what's what... and when I saw that hideous cluster of wires soldered together I thought perhaps this isn't JVC's handy work...

So what do you think it was ? - I'm going to remove it in due time and see If it has any bearing on making the CRT in this machine accept a signal, which at present it cannot, no snow or hiss and I think ( see attachment of the RF tuner ) that with the RF tuner case being snapped away like that perhaps this mod wasn't the best idea in the world...

Anyway the chip/IC on board there is a "Hitachi HA1151"

 

[stynger007]

Hi, If you check the images below I'll explain...

Inside my newly acquired JVC 3090EN I found an after market modification which I think is an AM radio hack or possibly a TV mod, you see my CRT on the box is borked at the moment and I wanted to see what's what... and when I saw that hideous cluster of wires soldered together I thought perhaps this isn't JVC's handy work...

So what do you think it was ? - I'm going to remove it in due time and see If it has any bearing on making the CRT in this machine accept a signal, which at present it cannot, no snow or hiss and I think ( see attachment of the RF tuner ) that with the RF tuner case being snapped away like that perhaps this mod wasn't the best idea in the world...

Anyway the chip/IC on board there is a "Hitachi HA1151"

View attachment 52056View attachment 52057View attachment 52058View attachment 52059View attachment 52060View attachment 52061

The RF tuner case , you didn`t mention and assuming from your post , radio is not working as well? Are you able to contact the person you bought it from to verify the mod? Interesting!

 

[Obiw4n]

The RF tuner case , you didn`t mention and assuming from your post , radio is not working as well? Are you able to contact the person you bought it from to verify the mod? Interesting!

Hi, The radio is actually working, the RF tuner on the CRT seems inoperative as I can see it's metal box/case has been dislodged in multiple instances... so that's not good, the TV has horizontal/vertical deflection etc, I can also see an erroneous wire which has been soldered to the back of the TV tuner along with an electrolytic capacitor which didn't have the space inside that tuner case to handle it and may be part of the reason why the tuner-case is dislodged... I need to disembowel the machine to fix it really but I've been working in the cosmetic side of things ( see below ) which is my design for the metal fascia which was missing on my box...

I did ask the chap I got it from about the TV and he told me it was like that when he got it... I assume at some point either a CB radio or short wave radio or perhaps a TV station or two was intended to be received with this new mod, either way I'm going to remove it and hopefully bypass the RF tuner side of thins and directly install a composite video signal and hope the CRT is fine, then I may install an HDMI to Composite converter and on the back of the JVC install an HDMI slot... maybe just a composite port along with audio in etc... all good fun to do yet.

 

[Obiw4n]

If any of you have a 3090 and a spare moment, could you take the back off and track down where this wire go's ? ( see attached ) you don't need any technical knowledge ( I'm winging it myself ) but there is this wire you see, part of the original JVC tuner circuit which was cut to install some kind of modification years ago... I've since removed it ( I think it was a TV modification of some-kind ) and I'm basically trying to get a signal to the CRT/TV... I've got sound, I'm just not sure where this rogue wire is supposed to go... it's quite a long which which go's from the right side of the machine over to the left side and into the RF tuner I think... but where ? anyway I'll ask around and experiment myself, but I'm close to getting this fixed and any help would be a boon.

The wire ( if you decide to take this mission ) is located on the right at the top, it's part of the TV board, it's white and if you remove a screw from a plate holding in the TV board you can remove the board, pull it back slightly and you'll see it... then follow it around to the left of the machine, it'll go past the CRT/tube and into the depths of the tuner I fancy which is the bottom board on the left, above it is the radio gubbins, but below the secret is in that TV tuner...

:Obi

 

[Obiw4n]

Actually... you may not need to have a look inside as I have a cunning plan, when I took out this old TV modification that time forgot I made a note of the plug type and the pins, basically what wires went where...

The TV part of this JVC 3090 in terms of vision & sound had been intercepted by this modification, so after removal I managed to work out what go's where... got the sound back ( hiss ) and I'm just about to ( hopefully fingers crossed ) get my TV picture back other than lines across the screen... or rather the familiar 'snow & hiss' you get when you have no aerial plugged in the back... anyway I'm just having a coffee and having a think then I'll attempt the fix, if it works then cool, I have an RF modulator which has an HDMI input and that via a coax cable plugs into the back of the 3090, quick bit of tuning and bobs your uncle... hopefully.

 

[Obiw4n]

It didn't work for me ( this is a diary of sorts ) I'm sure the modification I removed had a connection to the V.IF ( "Video Intermediate Frequency" I guess ) point on the tuner board.... and the broken connection I mentioned in my previous post which I needed to reconnect a connection to "V.IF.DET.OUT" ( Video Detection after demodulation from the RF tuner ) anyway it's the same after the connection...

I did connect an RF modulator and I tuned in the sound but the picture was just lines... but I'm sure I made the right connection from the tuner... oh well makes me think why this modification was there in the first place... perhaps the RF tuner was faulty... anyway I'm going to have to keep trying... next is composite... a baseband CVBS signal straight into the "V.IF.DET.OUT" on the TV board which controls the CRT/tube... bypassing the tuner entirely hopefully...

So I've bought a simple HDMI to Composite converter to test this out with which will arrive next week... sound wise I could just follow the path the tuner took into the amplification board.... I'll hack an RCA lead to give me the earth and the hot pin to wire into the TV board and fingers crossed it'll work...

:Obi

 

[Obiw4n]

There you go... composite video input into the JVC-3090, I think I need to add a 75 ohm resistor to the feed, not sure... but it works, the picture is stable but it has lines and it's a bit washed out, still I'll keep working on it... I hope eventually to out an HDMI input into the back and the converter box inside running off 5v as soon as you press the TV button... cool

:Obi

 

[Obiw4n]

After delving deeply into the realms of CRT diagnosis & repair I've managed to discover why my picture looks like gash...

The lines going diagonally across the screen are called 'retrace lines' and you shouldn't be able to see them obviously, 'the blanking circuit' in most CRT's is to tackle this problem and so if you see those lines something's wrong either with a component on the board or a voltage is too high on the 'flyback transformer' which in my case on this JVC I don't think you can adjust... or it could be just cracked solder joints on the board making for bad connections, it's a boom-box which I assume has been lifted then put down a few hundred times and I assume this could have rattled the innards somewhat.

I've fixed the cassette door also, it was opening... well not at all really, it's a simple plunger mechanism in a tube, the plunger has a rubber grommet near the tip which is just the right size to allow the cassette door to slowly pull the air out of it's tube... but over the years the rubber grommet had expanded because of over heating perhaps and thus the pressure brought to the plunger was too little as the door wouldn't be heavy enough to slowly pull the plunger... anyway I removed the rubber thing and boom... opens in less than a nanosecond... but hey... I may change that...

And lastly... I think If I can get this blanking circuit or voltage thing sorted on my CRT then my composite mod would look great as It would bypass the RF tuner, so what I'd do is wire up an HDMI plate on the back and that would feed the converter box and that would be it... get a little AC/DC 5v transformer in there and wire up a Bluetooth mod and seeing as the RF tuner would be made redundant I may replace that section with a mono-LED VU meter display... why not go hog wild... but tasteful... so yea, wish me luck, I'll post my progressions.

 

[Brutus442]

Very informative thread...thank you!

 

[Obiw4n]

Just a quick addendum on my plight to fix the CRT portion of my JVC 3090EN...

I replaced some electrolytic capacitors on the board but it didn't help... so I'm waiting on a couple of high voltage ceramic capacitors which feed the so called 'grid voltage' in a typical CRT... sometimes known as the 'G2' voltage... once they arrive I'll put them in fire her up and hope for the best... or try try again as the saying go's... but even if I couldn't fix the picture I could still wire up the vertical yoke wires on the tube itself into the sound amp and boom... an oscilloscope which moves with the music... there are some tutorials on how to achieve this on-line, so at the very least the old girl with her wonky eye could yet dance at the party.

I'll keep you posted, cheers

 

[Rein]

Informative thread. Just bought mine and already I'd get pumped by your mods. I'm no electrician but I love to learn. Btw, do you have both side of the facia template? Do you mind sharing the file? Mine is in terrible shape.

 

[Obiw4n]

check the attached files, some for printing, some for editing in Photoshop, I printed mine on sticky vinyl (see picture) I had a tough job getting the old glue spooge off the plastic, has to be smooth really or the final vinyl sticker catches the light on bumps and imperfections on the plastic, so it all needs to be flat, or print on something else, maybe sticker type paper, either way you have to cut the holes out, my printer shop did that for me using a machine, these photoshop files have the 'holes' marked out in a layer in the photoshop files, hopefully you can make good use of them... cheers

:Obi

 

[docs]

Great job on this, hope you get the crt sorted.

 

[Brutus442]

As a 3090EN owner myself, all I can say is thank you for the detailed experience you've undertaken and valuable files you've included. Cheers brother!

 

[Rein]

to me this JVC is the most "handsome" looking Boombox ever made. Thanks for the files man.... I'm no expert in Photoshop