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Old 15th Apr 2019, 8:55 am   #1
1976saint
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Default Aiwa HT-DV90 Help (no power)

After the successful help/diagnosis and repair of my old AKAI AA-RL1 AMP (https://www.vintage-radio.net/forum/...d.php?t=154464) my next project is to get my old Awia HT-DV90 working again. I'd like to use it again as a CD-Player to go with my newly working AMP.

It had a problem firstly that it didn't read disks anymore but that was fine as I primarily used it for TV surround due in most part to it's dual OPTICAL Inputs!

Then one day it wouldn't power on. I put it in storage and a few years back but recently took the lid off and found that the FUSE F604 had blown.

So not being good at electronic circuit diagnostics (but handy with a soldering iron) I turn to you guys to once again help point me in the right direction as to where to start looking please.

I've attached the service manual (which I found free this time) and photos of the power PCB. Note the underside which look to be some kind of capacitor maybe which do not look great.

https://www.manualslib.com/download/...a-Ht-Dv90.html

Kind Regards
Paul
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Old 15th Apr 2019, 5:31 pm   #2
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Default Re: Aiwa HT-DV90 Help (no power)

Well if it's banging fuses start with the filter block and look for shorts or leakages, that’s the bit between the mains input CN61 and the rectifiers BD62-BD63.
Check the rectifiers as a diode might have gone short. Check the chopper FET Q234 for shorts leakage.
It's also possible that one of the controller IC's has failed IC57-IC66.
Check D662 and Q617 if these are having problems they could have destroyed IC66.

These are the first few checks I would do. Good luck
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Old 15th Apr 2019, 6:09 pm   #3
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Default Re: Aiwa HT-DV90 Help (no power)

Another thing I should have mentioned, if it's a glass fuse and it has gone all black your going to have to do some fault finding
but if the fuse has a small break in the wire you might be very lucky and just be able to change the fuse.
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Old 15th Apr 2019, 9:05 pm   #4
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Default Re: Aiwa HT-DV90 Help (no power)

If nothing has obviously gone bang or cooked then I would certainly try another fuse. They do degrade with time and eventually fail during the switchon surge.

If the new fuse blows immediately then you do indeed have a more significant fault, and the player is likely to be BER. It does look as if something has got very hot under the PCB, but the photo may be misleading.
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Old 15th Apr 2019, 11:39 pm   #5
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Default Re: Aiwa HT-DV90 Help (no power)

Thank you for the advice, I'll take look at the parts advised. The fuse was black (gone bang) unfortunately!
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Old 16th Apr 2019, 7:29 am   #6
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Default Re: Aiwa HT-DV90 Help (no power)

Are those two jumper wires on the underneath of the PCB factory or a bodge? Check them against the schematic.

What are the voltages the PSU supplies? It may be possible to find another SMPSU that will fit to save fixing this one, although of coarse the rest of the device will need checking for shorts before powering up with a new PSU.

Andy.
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Old 16th Apr 2019, 8:21 am   #7
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Default Re: Aiwa HT-DV90 Help (no power)

The two jumper wires underneath look to be a couple of components covered with a plastic sleeve. They have a bit of resistance when I put a meter over them. They are not on my schematic, the version of the HT-DV90 is the K variant possibly which could stand for UK (and would make sense)?

I guess there could be another SM around showing them but I've not come across any as yet.

Searching the web for this unit is also proving pretty elusive atm.

@paul , I think I might have tried a new fuse when I first looked at the problem but I can't remember as it was about a year or so ago. The blacken part of the board your referring to is melted black sleeve (but cover two unidentified components) it looks like and around the base of the big capacitor solder point. I'll take another pic for a better look-see.

Paul.
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Old 16th Apr 2019, 9:24 am   #8
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Default Re: Aiwa HT-DV90 Help (no power)

Photos of jumper bodge components, and burn marks attached.
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Old 16th Apr 2019, 10:13 am   #9
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Default Re: Aiwa HT-DV90 Help (no power)

It could be that that is a factory modification made during the production run after some problem was identified. It's not uncommon to find components soldered onto the wrong side of a PCB. The work doesn't look very professional though.

I've no idea what the components are or whether they've overheated, but the third pic doesn't look good with what appears to be melted solder.
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Old 16th Apr 2019, 11:44 pm   #10
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Default Re: Aiwa HT-DV90 Help (no power)

I'd agree it does look like things have got a bit hot there. I wonder if they were (underspecced) resistors that have been getting hot and going progressively lower in value/passing more current/getting hotter until they've reached a runaway situation and popped the fuse.

If the apparent heatshrink(?) could be removed and they are in fact resistors, and still readable, then I might lift them out of circuit and check their values.

The only other thing they look like to my mind, is small inductors that I've seen in a package similar where the bodies look to be covered in tubing like that. Doesn't look healthy though.
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Old 17th Apr 2019, 1:18 am   #11
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Default Re: Aiwa HT-DV90 Help (no power)

Looks like there's some glue there attaching those track side resistors which has turned conductive. Remove it all before attempting to power that up again.
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Old 18th Apr 2019, 5:55 pm   #12
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Default Re: Aiwa HT-DV90 Help (no power)

Hello,
When looking at the pictures posted I first thought they had put some avalanche protection diodes across the output
of the rectifiers but after enlarging the picture and putting my glasses on I can now see that they have paralleled the
outputs of the rectifiers, possibly via two low value resistors? I have not seen this done before, I imagine it's maybe
done to share the current as one rectifier is rated at 1 amp and the other is rated at 4 amps so maybe the one rectifier
was a bit borderline. Or maybe they need to share the reservoir capacitance, it's not clear
I don't see why it needs two rectifiers anyway, it obviously didn't work very well if they had to strap them together
after manufacture.

If that board burn between C653 and the link wire is a piece of track blown out then it's possible that IC67 has failed.
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