Harman Kardon EQ8 - Recap

[jheu02]

Just a quick project for tonight. Picked it up at GW along with a 490i receiver the other day. Checked it out and the functions seemed to work so I decided to keep it. Quick listening test showed it robbed a little detail from the music when the EQ was active as opposed to it just looping back to the amp with the EQ off. A recap of this was going to be a winter project, but curiosity got the better of me so I opened it up to see what the insides looked like. Pretty empty and not too many caps, so I checked my stock and decided a quick redo was in order.

I had downloaded the SM and looked at the schematic and noticed that some of the lytics were directly in the signal path. So, these were going to get audio, film, or UKL caps depending on value, etc. The photos show these audio path caps to be the purple sleeved ones which are Matsushita caps (Panasonic).

I've had problems with these caps in other gear so knew they were coming out, but it somewhat answers a question I posed in another thread as to what series caps these purple ones were. They're either Panasonic's equivalent of a low-leakage cap or audio cap for future reference. Anywho, after pulling them out I discovered several with corroded leads (just like in other gear) and 2 were open. So, if found in any gear you restore, REMOVE AT ONCE. They are problems waiting to happen.

Without further ado...

Before

After

 

[avionic]

Excellent photography..High Def sure shows the dust. Need a swiffer..

LOL

Looks pretty nice.:thmbsp:

 

[roger2]

Pics do look good. How do you do lighting for these shots?

 

[jheu02]

Two bulbs in light stands with reflectors (similar to aluminum clip-on work lights). Camera white balance corrected for tungsten light. 2" timer for mirror lock-up. DSLR on a tripod. The shot of the cap corrosion also used a 13mm extension tube on the lens since it was a macro shot.

Photography is another hobby of mine.

 

[jheu02]

Just a quick update on this recap project. I put things back together tonight and gave a listen after the dim bulb test checked out OK. The openness and detail in the music was back and evident post recap. I can't be sure it was veiled due to the two open caps (both 10uF/16V) or some that were leaking (not getting up to rated capacity and decreasing right away), but it sounds better now than it did prior to the recap.

 

[KenP]

Thread revival! I picked up one of these on ebay and found exactly the same thing on those 10mf caps, they seem to leak alot and it makes the solder much harder to melt. Check those fuse resistors too mine were way out of spec.

 

[jsettecase]

Thanks for the post and the great pics! I JUST picked-up one of these on eBay. This thread is EXACTLY what I had in mind when I bought it. I downloaded the manuals so I could do the same re-cap. This unit has very good specs, but the old caps gotta go for sure. I believe its a high quality HK product (back from an era when HK was at its best) that's worth restoring. As long as the Slider Pots are in good shape. Did you have any issues with the Sliders? The guy I got it from says he's sprayed them(and switches) and they work without any crackling or dead spots. I will re-post once I finish this project, although my bench is full of Hafler DH-500 amp upgrades right now, so it will be on the back-burner for now.
I started working with a guy on eBay that was an amplifier Engineer with Dynaco and Hafler for 18 yrs. and over the years, he has developed his own Driver board upgrades for Hafler amps. These upgrades are VERY affordable and yield phenomenal results! After I did my first DH500 upgrade/rebuild for a friend, We were blown away! My friend says, " Its the best sounding amp he's ever heard." I agreed and I was hooked. If anyone is interested, search "Hafler Upgrade" and you will find my (eBay member: 7houses) "Installation Only" listings as well as QUA-CO's "Hafler Upgrade Kits". Ed at QUA-CO Audio doesn't do any installation work, so he and I have teamed up. Buy the parts/kits from Ed and I'll put them in.

 

[jheu02]

I did not have any issues with the sliders. Welcome to AK.

Please make sure you read the rules about advertising your sales/services. It's kind of bad form to turn someone else's thread into a sales pitch for some other thing.

 

[jsettecase]

I did not have any issues with the sliders. Welcome to AK.

Please make sure you read the rules about advertising your sales/services. It's kind of bad form to turn someone else's thread into a sales pitch for some other thing.

Sorry, John. Thanks for the warning. It was just my excitement over my projects bubbling into my post. Can I edit that out of my post so as not to cause a problem?

 

[jheu02]

I thought that might be the case. I know as a subscriber I can edit my posts, not sure if just as a member. Try and see if you can.

 

[jsettecase]

I thought that might be the case. I know as a subscriber I can edit my posts, not sure if just as a member. Try and see if you can.

I couldn't find an 'edit' link anywhere. If the message has just been posted, there is an 'edit' link, but I think once you log out, it can only be viewed.

 

[JimL1]

Just a quick project for tonight. Picked it up at GW along with a 490i receiver the other day. Checked it out and the functions seemed to work so I decided to keep it. Quick listening test showed it robbed a little detail from the music when the EQ was active as opposed to it just looping back to the amp with the EQ off. A recap of this was going to be a winter project, but curiosity got the better of me so I opened it up to see what the insides looked like. Pretty empty and not too many caps, so I checked my stock and decided a quick redo was in order.

I had downloaded the SM and looked at the schematic and noticed that some of the lytics were directly in the signal path. So, these were going to get audio, film, or UKL caps depending on value, etc. The photos show these audio path caps to be the purple sleeved ones which are Matsushita caps (Panasonic).

I've had problems with these caps in other gear so knew they were coming out, but it somewhat answers a question I posed in another thread as to what series caps these purple ones were. They're either Panasonic's equivalent of a low-leakage cap or audio cap for future reference. Anywho, after pulling them out I discovered several with corroded leads (just like in other gear) and 2 were open. So, if found in any gear you restore, REMOVE AT ONCE. They are problems waiting to happen.

Without further ado...

Before

After

I couldn't find an 'edit' link anywhere. If the message has just been posted, there is an 'edit' link, but I think once you log out, it can only be viewed.

 

[JimL1]

I just did a restore on a Harmon just like the above and found that the (CE) 10uf 16 volt and a couple of other purple caps had leaked so badly in 3 places had eroded the circuit board. I have restored many units of vintage audio and have never found a capacitor that had leaked so badly that it deteriorated and ate the circuit board traces. I had to replace in some areas with jumper wires. When I first purchased the unit I had low output (about 25% in left channel) the caps helped a bit but still same issue. I did find Q101 did not read the same with Q102 with ohm meter. I am guessing it was damaged by faulty purple caps. The capacitors below the long plastic toggle switch extenders are a bit hard to get to but replace all now will look for a new transistor for Q101 and hope i can find a replacement. Finding an exact transistor is usually always a deal breaker.

 

[jheu02]

Are you sure it's bad? Q101,102 are 2SK363BL according to the service manual. FETs don't test the same way as bipolar Qs.

Datasheet and possible subs if it is bad

 

[JimL1]

Are you sure it's bad? Q101,102 are 2SK363BL according to the service manual. FETs don't test the same way as bipolar Qs.


I did replace the bad transistor. Yes it was a j fet. The channel now works and is equal to the other channel. I did notice that when I change the Left and right potentiometers that have a red overload signal indicator I can never get either channel to overload and the leds to turn on. I don't know how they are expected to work if they are supposed to flash red once in awhile or not normally come on. Anyway I probably won't spend too much more time on this eq. Thus far I am not real impressed with it's quality. It does sound ok though.