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View Full Version : Whats up with this JBL 6230?



Russellc
01-19-2008, 07:23 AM
Whats up with this JBL 6230? Just won this off of Ebay. It appears to be very clean inside and out with hardly any scratches. Examining the circuit boards for any repairs, I only see a couple, but they present a question.

I can see in the middle towards the back a device made of clear plastic that appears to be a timer or relay of some sort, looks like it has been replaced. I understand it is typical of these amps to need to replace this part after all these years.

There is some soldering around the pins of the power supply caps, but then there is this wire soldered near the same pad, that goes back to a smaller circuit board. (These observations are viewed from the bottom) Is this wire normal, or what is going on here? This wire is the one thing that concerns me that I can see, anyway. Perhaps an added ground wire? The power supply caps appear to be the correct ones, May be they were replaced, or need to be? That funky white resistor doesnt look original either, anyone have this in theirs?

I am unable to fire this thing up until I get some connector cables, it is supposed to be tested and working, what ever that means.

Any help from anyone with a 6230 would be greatly appreciated. Is this wire normal, an added ground or what?

I have included some pics of this "mystery wire".

Thanks for any help, Im a tube guy
Russellc

hjames
01-19-2008, 07:50 AM
The clear plastic case thingee is a start up relay. It disconnects the speakers so you avoid getting a loud THUMP when you first power up. Thats a good thing! Other folks may have better info about the added ground wire.

My first 6260 had a line like that but it had other problems and was all burned up inside (it was an ebay ripoff!)
http://audioheritage.org/vbulletin/showpost.php?p=175886&postcount=1

But I got better amps later and all is fine now
http://audioheritage.org/vbulletin/attachment.php?attachmentid=27770&stc=1&d=1188706795

Russellc
01-19-2008, 08:01 AM
The clear plastic case thingee is a start up relay. It disconnects the speakers so you avoid getting a loud THUMP when you first power up. Thats a good thing! Other folks may have better info about the added ground wire.

My first 6260 had a line like that but it had other problems and was all burned up inside (it was an ebay ripoff!)
http://audioheritage.org/vbulletin/showpost.php?p=175886&postcount=1

But I got better amps later and all is fine now
http://audioheritage.org/vbulletin/attachment.php?attachmentid=27770&stc=1&d=1188706795
Thanks for the reply. Going to your original posts for the pictures, I see yours had an added wire as well as the white mystery resistor. Fortunately, I dont have all the burned up stuff inside.

Does anyone know if this wire is normal, or what the purpose of the mod was? ( If it was a mod ) I would like this amp to be in perfect shape, and then add a 6260 for a biamp system when I go three way.

Again, any help much appreciated! Please!

Russellc

Russellc
01-19-2008, 08:19 AM
Photos of your 6230 internals appreciated. Anyone know of a tech in the Kansas City area that I could have look this thing over? I hate to just "fire it up" so to speak.

Any info on this wire, whether it belongs there or is some known mod, I see heathers old 6230 had one added as well.

Thanks,
Russellc

subwoof
01-19-2008, 08:39 AM
The "right to change design for improvements" clause comes into play here.

The thick black wire was added on later models because the DCR of the ground trace to the input connector board was too high. Unless you are well versed in star grounding techniques, it's a long story BUT it is supposed to be there along with that resistor. And relay.

I have 40+ of that series amp in the shop and most have that wire. And yes - I have heathers cooker and maybe this spring it will come alive along with her relay-challenged ( tough problem! ) 6260.

btw - post a picture of the other side of the board - there are 3 caps near the voltage regulators that should be replaced because they fail with age.

sub

Russellc
01-19-2008, 09:01 AM
The "right to change design for improvements" clause comes into play here.

The thick black wire was added on later models because the DCR of the ground trace to the input connector board was too high. Unless you are well versed in star grounding techniques, it's a long story BUT it is supposed to be there along with that resistor. And relay.

I have 40+ of that series amp in the shop and most have that wire. And yes - I have heathers cooker and maybe this spring it will come alive along with her relay-challenged ( tough problem! ) 6260.

btw - post a picture of the other side of the board - there are 3 caps near the voltage regulators that should be replaced because they fail with age.

sub
OK, have a look at these, if not clear enough I can take some macro shots
if that would help. what would it cost for a go through subwoof?

Russellc

subwoof
01-19-2008, 11:21 AM
Yup - your 3 caps are original ( they are the yellow cans ). One is for each of the low voltages ( +/-15v ) and the third for the 24V that runs the relay. They are the same size and ANY basic tech can replace them in a few minutes.

PM me for prices, etc - I have a bag of 100 here at all times..:o)

sub

matsj
01-19-2008, 05:05 PM
I have a 6230 with a small problem to. I have to wait 3 min for the relay to click.

mats

matsj
01-20-2008, 12:03 PM
My C29,C31,C32 caps are blue :) 470uf 50 volt in both of my 6230.

Picture:

Russellc
01-20-2008, 12:39 PM
I have a 6230 with a small problem to. I have to wait 3 min for the relay to click.

mats

When I was searching concerning my own problem, I ran across someone posting about this delay problem. Apparently it is a common problem after all these years and was easily remedied, by replacement I believe, cant really remember if it was the device itself or some associated components.

I was searching at the time for 6230 info, should be easy to find.


PS It was "Urei 6230 amp startup question" In which you posted in.....did you try changing the caps? sounds like this is the solution. Its an easy amp to work on.

Russellc

Russellc
01-20-2008, 01:00 PM
I finally made my way to a guitar center and aquired some cables to hook this thing up to my rca output preamp. On first fireup, this supposedly "Tested and gone through" amp was anything but. Very clean inside and out, but with the preamp controls ( a buffer/no gain line stage) had to be wide open to get any sort of volume, as well as the gain controls! Plus, one channel was noticeably quieter than the other. Then a hum started.

On Subwolf's advice I re flowed all the output device legs, all input joints and any other funny/dry looking joint I could find. I also used a regular ( tube) preamp with gain and now the volume was there, and all hum was gone, but one channel still lagged the other.

Then I accidentally bumped the power amp and the channels volume returned briefly. The top was still off, so I carefully nudged the timer/relay device and noticed that a tap on it would cause the channels volume to cut in and out.

Back to the solder station and reflowing things. When all looked good, I tried again, but now when I pushed on the timer nothing happened, just one channel louder than the other. In all this flurry I accidentally bumped one of the coils which are located right by this device, and it was apparent that this was the device with the bad connection, or that it also had a bad /cold joint.

Carefully reflowing that coil corrected the problem completely, Amp is singing for almost an hour with no abnormality. THANKS SUBWOLF! for
all your help on this. I guess the moral of the story, as told to me by Subwolf, is that these amps are built like a tank, but years of this amps giant transformer's vibration from humming away gradually messes with solder joints. They must be reflowed and its good again! Fortunately, for anyone that didnt know, both covers are removable top and bottom, so access is great.

Russellc

Russellc
01-20-2008, 01:53 PM
Does anyone hear know what the typical maximum dc is on the output of these amps? one channel measures 1 mv on one channel and 7 mv on the other.

Thanks for the info,

Russellc

subwoof
01-20-2008, 02:47 PM
no sea-faring speakers here - it's subwoof.

Ps - rule of thumb is anything less than 10mv DC is ok. The typical crown "D" series leaves here at .1 to 1 mvdc.

sub

sigh.....*update"

OWWWWWWOOOOOOOOOOOO (not)

it's subwoof ( like a dog - not a wolf )

me need beer :cheers:

Russellc
01-20-2008, 02:59 PM
no sea-faring speakers here - it's subwoof.

Ps - rule of thumb is anything less than 10mv DC is ok. The typical crown "D" series leaves here at .1 to 1 mvdc.

sub
Lord! I've got some editing to do. Sorry! and thanks again!

Russellc

Russellc
01-20-2008, 03:07 PM
no sea-faring speakers here - it's subwoof.

Ps - rule of thumb is anything less than 10mv DC is ok. The typical crown "D" series leaves here at .1 to 1 mvdc.

sub

What sort of things cause this slightly higher reading in one channel, or is this just the nature of it? Perhaps the new caps on the aforementioned regulartors might help? Or devices drifting with age? How often are they replaced in your experience? Whats require to get them both around 1 mv?

Russellc

clubman
01-20-2008, 03:11 PM
If you want it checked out you can try this place,

http://www.prestonelectronics.com/index.html


I know he services Crown, not sure about ueri/jbl amps.

Lee's Summit area

Very reasonable prices

subwoof
01-20-2008, 03:19 PM
the way the circuit is designed is what determines the output offset. Some amplifiers use a trim pot on the input stage to introduce / correct any offset that happens to make it to the output.

The IC's used in the "D" crowns have no internal compensation so they naturally need some "correction". The urei's use TL074's which are internally compensated.

Replacing the power supply caps won't change it.

And remember like your car's front end ( and the other half's ), things tend to settle with age but not all need adjustment.

I *just* know I'm gonna get killed for that one....:)

sub

Russellc
01-21-2008, 01:43 PM
Good enough then. It is working fine no glitches.
Seem to show just a little hum when hooked up to my Altec A7 s. Is that just the deal with high efficency speakers,( I didnt notice it with other speakers on hand with 89- 90 db effciency.) or can this be quieted to any degree? Its not obnoxious, just noticable in use when it gets quiet. Plus, I was using a tube pre amp, will try it direct connected to a cd player next to see.

Thanks,

Russellc

subwoof
01-21-2008, 02:34 PM
You have a slight ground loop. There are numerous postings on this site which go into detail.

remove the strap that is in the middle of the terminal input bar.

If still there, use a cheater on the AC plug - but SOMETHING in the system has to be connected to AC ground

sub

JBL 4645
01-21-2008, 03:33 PM
The clear plastic case thingee is a start up relay. It disconnects the speakers so you avoid getting a loud THUMP when you first power up. Thats a good thing! Other folks may have better info about the added ground wire.

My first 6260 had a line like that but it had other problems and was all burned up inside (it was an ebay ripoff!)
http://audioheritage.org/vbulletin/showpost.php?p=175886&postcount=1

But I got better amps later and all is fine now
http://audioheritage.org/vbulletin/attachment.php?attachmentid=27770&stc=1&d=1188706795

That is a good thing but never take it for granted always power up additional PA equipment first otherwise you’ll hear that thumping sound! And always power down the amplifiers first otherwise there's a slim chance you’ll hear that thumping or popping sound!

Wasn’t the JBL 6230 6260 and 6290 produced around the late 1980’s?


You have a slight ground loop. There are numerous postings on this site which go into detail.

remove the strap that is in the middle of the terminal input bar.

If still there, use a cheater on the AC plug - but SOMETHING in the system has to be connected to AC ground

sub

I’m thinking about taking a chance with the Behringer MICROHD HD400 at a later point in time, you’re not the only one with this embarrassing humming sound; it’s a pain in the neck.:banghead:

http://www.behringer.com/HD400/HD400_medium.jpg
http://www.behringer.com/HD400/ (http://www.behringer.com/HD400/)

Russellc
01-22-2008, 02:58 PM
What about replacement parts for these (6230,6260,6290) amps? Are the outputs, or more importantly, the input devices, are they still available? or good substitutes? Would be nice to be able to replace if they begin to drift and DC goes up.

Thanks,
Russellc

subwoof
01-22-2008, 03:55 PM
The only "special" transistors on the amplifier are the small signal ones and they are readily cross-referenced. Everything else is off the shelf..:o)

Good engineering means you use what is common in 1981 and what WILL be common in 2008.

:cheers:

Russellc
01-23-2008, 07:25 AM
The only "special" transistors on the amplifier are the small signal ones and they are readily cross-referenced. Everything else is off the shelf..:o)

Good engineering means you use what is common in 1981 and what WILL be common in 2008.

:cheers:
Amen to that. The more I look at this amp the better I like it. what a pleasure to work on, very easy to get to everything, and very bullet proof.
Cant wait to find a 6260, then i will have to go through my abused 5234 crossover!

Russellc

Russellc
02-01-2008, 07:23 AM
My C29,C31,C32 caps are blue :) 470uf 50 volt in both of my 6230.

Picture:
Could you post a pic of the "solder side" of these caps? Particularly the small ones next to the regulators w/ heatsinks.
Thanks,
Russellc

GordonW
02-01-2008, 08:48 AM
WRT output relay problems on 6230s and 6260s- I had one here, that I had to get up and running, kind of emergency status, for a gig here.

Found out the relay was intermittent... didn't have one here, and couldn't get the relay cover off. Out of desperation, I took a small drill bit and drilled about a 1/8" diameter hole in the top of the relay cover, and sprayed a dose of Rid-Ox into the relay, until it ran out the bottom. Then, with speakers disconnected, I turned the amp ON and OFF about 20 times in succession, waiting for the relay to click in and out each time.

Hooked up the speakers... MIRACLE of MIRACLES, it worked PERFECTLY.

In fact, it worked so well (CONSISTENTLY!) that I still haven't changed that relay, even now... I just put a little putty over the drilled hole, to keep additional gunk out...

Not the ultimate long-term solution, obviously... but it's certainly WORKING FINE here...

Regards,
Gordon.

subwoof
02-01-2008, 10:07 AM
When the relays denergize, and there is a load ( and signal ), there is a small ARC ocross the opening contacts. Basic spark-gap theory. Most speaker loads are inductive so there will be an EMF generated across on opening of the circuit.

An old relay trick from the early 1900's is to put a small magnet that pulls the arc away to the side. JBL/UREI did this BUT the glue goes bad with age and many of them have fallen off. look around the chassis and see if they are hiding. Don't worry about polarity - just glue them back on.

Even then there will sometimes be a noise because the contacts are pitted. In serious cases where replacement isn't feasible get a relay file and burnish the contacts.

Unfortunately this removes whatever plating was there so it needs to be repeated over and over. This is what old-line telephone techs did for the relay switching stations before the transistor era. In 1975 I went into an AT+T long distance room with hundreds of 6ft tall racks just chock full of relays all in motion. There was one tech for each row/bank with a file, oil can and a small assortment of parts. All those jobs went the way of the buggywhip.

But if you do the goo like gordon did, you do not lose the plating and possibly it's life will be extended....:)

Amplifiers that have cycled on + off MANY times under full load will of course be worn out earlier and I have seen a few relays with actual mechanical fatiguing of the wiper arms and pivot points.

rotsa ruck rouie ( apologies to scooby )

sub

grumpy
02-01-2008, 12:31 PM
An old relay trick from the early 1900's is to put a small magnet that pulls the arc away to the side. JBL/UREI did this BUT the glue goes bad with age and many of them have fallen off. look around the chassis and see if they are hiding. Don't worry about polarity - just glue them back on.

Wondered what the, uh, heck a small magnet was doing inside a chassis
lid (loose). Small, circular disc ~ 3/8" diameter? Now I have to remember
which chassis and see if I still have the magnet. :p Thanks! -grumpy