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Vintage Koss HV/2a's opened up!!! PICS!! + Need help w/ repairs.

post #1 of 20
Thread Starter 
I have had and old set of Koss HV/2a's for a while now, and only now have I decided to do something with them.

They worked in one side, and they sounded pretty good as well. So today, I decided to open up the non-working side to see if I could get them working again. It was not easy... There were no screws, so I had to do allot of knifing...

The driver inside is like nothing I've ever seen (but I haven't seen much so that doesn't really mean anything ), and is a sort of dome shape. I can see the connectors where the cable goes to, and it seems to look fine.



What else should I be looking for to try and fix it? Is it worth fixing, or should I try sending it back to Koss and make use of the lifetime warranty (lol)?

Some more pics:


^ driver under driver cover and bit of the casing...

^ drivers and driver cover...

^ back of the drivers...

^ money shot!
post #2 of 20
Looks like a dynamic driver in some kind of housing. The agenda for now would be:
1. Measure resistance between the two points where the wires enter the driver housing. The value should be about the same as for the working side when measured at the plug. If there is no connection at all, you have a Real Problem[tm]. Otherwise it's just the cable screwed up somewhere.
2. Find some foam to replace the stuff with obvious crumble-to-dust syndrome (about equal thickness and density).
post #3 of 20
I concur with sgrossklass. You've got to hope for a cable issue, as it'll be extremely difficult to get a new driver. A lot of intermittent connections are cable-related, though, so your odds are alright.

No point in sending it back to Koss-- the lifetime warranty program started in 1989, and these were bought before that. Even if you paid for a repair, they'd just throw these away and send you one of the current lineup.
post #4 of 20
Ohm out the cable.... check for wire continuity between those solder posts and the TRS connector.

Ohm out the driver, measure across the driver solder posts. It should be close to the spec'd impedence of the cans. If it is in Meg-ohms you have a cooked driver.
post #5 of 20
Thread Starter 
Ok... So how do I 'ohm' it and measure the resistance? I have a voltage tester thingy... Could that be used to do this?
post #6 of 20
send it back with the $7 fee and koss should replace it.

i sent back a pair of ~30 year old koss pro/4aa's and they were repaired:

http://www6.head-fi.org/forums/showthread.php?t=123263

BUT the ones i sent back were re-released fairly recently, so they probably had replacement parts on hand.

if they don't have the parts to replace yours you may end up getting a 'comparable' model. not sure if that's something you'd want.
post #7 of 20
Thread Starter 
I think I'd prefer to try and repair them myself if possible, rather than getting a replacement...

If I cant repair it, do you think they'd still replace it when the casing has been slightly mutilated to get to the drivers?
post #8 of 20
Thread Starter 
Quote:
Originally Posted by kramer5150 View Post
Ohm out the cable.... check for wire continuity between those solder posts and the TRS connector.

Ohm out the driver, measure across the driver solder posts. It should be close to the spec'd impedence of the cans. If it is in Meg-ohms you have a cooked driver.
W00t! Just found a multimeter. Only problem is, I'm not REALLY sure how to use it...

It is exactly the same as this one here (http://www.dse.co.nz/cgi-bin/dse.storefront/457cdd5e015ea7b42741c0a87f3306ef/Product/View/Q1467)[/url], and says it can measure resistance (I think thats what I need to do).

When I touch one wire on the red solder point and the other to part of the TRS, heaps of numbers jump around on the screen, and it never seems to stay still. Why is this? How can I stabilise it? Do I have it set on the wrong setting (its set to the 20m setting on the ohm side)?
post #9 of 20
Thread Starter 
*bump* still need help fixing them...
post #10 of 20
What's the number stay around? In the measure of current, voltage, or resistance/impedance, the measurement is never stable. 20m means 20 million. The figure is in the millions of ohms.
post #11 of 20
Thread Starter 
Quote:
Originally Posted by jmmtn4aj View Post
What's the number stay around? In the measure of current, voltage, or resistance/impedance, the measurement is never stable. 20m means 20 million. The figure is in the millions of ohms.
When its on 20m, it doesn't seem to work very well.

I put it on 20k, and it came up with around 17 ohm, on the 20k setting. Is this good?
post #12 of 20
Try the 2kOhm range (or 200 ohm, should the result be lower than that). One would normally expect something between 32 and 600 ohms. The other channel should post a similar result.
post #13 of 20
Thread Starter 
Quote:
Originally Posted by sgrossklass View Post
Try the 2kOhm range (or 200 ohm, should the result be lower than that). One would normally expect something between 32 and 600 ohms. The other channel should post a similar result.
WOW. Its jumping around allot. It jumps around in between 2 and 1000.... Is this supposed to happen? Maybe I need a new multimeter (this one is a cheapo $5 one...)
post #14 of 20
are those voice coil wires in the first pic? if they are, then I'm guessing it's borked. I don't think the phones qualify under the warranty, it says on the Koss site it applies only to phones purchased after July 1989.

They *may* repair them, but is the cost worth it?
post #15 of 20
Thread Starter 
Quote:
Originally Posted by craiglester View Post
are those voice coil wires in the first pic? if they are, then I'm guessing it's borked. I don't think the phones qualify under the warranty, it says on the Koss site it applies only to phones purchased after July 1989.

They *may* repair them, but is the cost worth it?
Yeah they are voice coil wires... They fell out when I opened it lol... So that side is broken for good ? No way I can fix it
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Head-Fi.org › Forums › Equipment Forums › Headphones (full-size) › Vintage Koss HV/2a's opened up!!! PICS!! + Need help w/ repairs.