Topic: 1176ln dark unit ? (Read 6361 times)

Buzz · « **on:** April 26, 2006, 07:37:19 PM »

After reading the Ebay thread this came to mind , I bought 2 1176ln's ( silver face ) of Ebad 2 yrs ago and one has always been slightly darker sounding than the other one ( they are about 200 apart in the S/N's ) they were bought as a pair way back when by a radio station I believe ( at least that was the story ?? )

I tend to use the brighter unit most of the time , the other unit seems to respond differently to the same source/settings I did by the stereo adaptor fr them but have never really tested them together.

Anyhow the talk about the caps has me wondering
1. What should they be ( Ducati ? )
2. What would be the best way to test the unit ( I have a scope and other test equipment available and I have 30+ yrs in electronics )
3. Where would I source the caps if needed ?

Thanks Guys
Later
Buzz

David Kulka · « **Reply #1 on:** April 26, 2006, 11:15:15 PM »

I would start by just checking the frequency response. If one of them really sounds darker, that should be easy to measure. Maybe check headroom, while you're at it. If one of them is out of spec, have it serviced.

An original 1176 that hasn't been recapped is probably not performing as it should. If either or both has never been recapped then all bets are off, and that's where you should start. Most modern caps are of very good quality, replacements are easy to find at Digikey, Mouser, etc.

Wayne Kirkwood · « **Reply #2 on:** April 27, 2006, 09:39:25 PM »

They will open up sonically with recapping and not just on the low end. Replace all of the electrolytics coupling and bypass. If I'm not mistaken - and I should check my notes - there was one cap that was installed backwards in terms of polarization. The schematic was also wrong but the units I recapped always measured reverse polarity on this one cap. It takes about maybe 2-3 hours to pull the board, recap, locally deflux and reinstall. I know people have their own preferences in cap brands but chances are just about any cap is better than the 25-30 year old ones in there. I used Panasonics from Digi-Key.

Edit: I had forgotten that the bottom cover comes off and that it didn't set down in a pan. zmix is right: This is very easy to do. You won't regret doing it at all. There's no "magic" in those vintage caps. I checked a schematic and didn't find the reverse polarized cap but there were quite a few revisions. As I recall it was an emitter bypass electro. I'll keep looking.

zmix · « **Reply #3 on:** April 27, 2006, 10:26:18 PM »

Actually, the chassis bottom unscrews (as you can see here) and the whole operation is quite painless.
index.php/fa/2726/0/

J.J. Blair · « **Reply #4 on:** April 28, 2006, 08:32:49 PM »

Chuck, is that a blue stripe model?

zmix · « **Reply #5 on:** April 29, 2006, 01:38:45 PM »

...from 1968.....YEAH BABY, YEAH!!!
index.php/fa/2733/0/

Brian Roth · « **Reply #6 on:** April 30, 2006, 02:17:34 AM »

Besides the 'lytics, I suggest also replacing those internal trimmer pots. I've seen more than a few that were flaky or worse.

Bri

Jim Williams · « **Reply #7 on:** April 30, 2006, 02:33:01 PM »

Also those transistor sockets get oxidized and corroded. Replace them with machine sockets from Millimax or just solder them in.

zmix · « **Reply #8 on:** April 30, 2006, 06:52:47 PM »

er... that was a 'before' picture I took... it's SO vintage..!

So... how many techs does it take to change a capacitor?

Buzz · « **Reply #9 on:** May 08, 2006, 01:31:52 PM »

Thanks Guys I'll try recapping the dark one first just to be able to compare the 2 side by side again , I will also check the xstr sockets and pots ( without changing settings ) I am expirienced with electronics so no prob there. And keep an eye on the backwards cap !!!!!!! I have 2 of them to compare to each other so that will help

Later
Buzz

Anybody had any success using the stereo adaptor box from Urei ??? I have one but the units sounded SO different I never hooked it up

Buzz · « **Reply #10 on:** May 08, 2006, 06:30:41 PM »

Another quick question I checked the unit S/N 8554 Rev H model , the schematic shows the input caps to be Tantalum but they are actually electrolitics ????? strange , so any difference between the 2 regarding signal ? or freq response ? I know there is a definite difference in the construction of the caps but I have no expirience in swapping the two in an audio circuit.

I did not order the mica caps for the unit ( they should last a million years !!!! hell they are mica )

I will post the parts I ordered from mouser in case anybody needs the P/N's

LAter
Buzz

Brian Roth · « **Reply #11 on:** May 08, 2006, 06:56:46 PM »

Buzz wrote on Mon, 08 May 2006 12:31

Thanks Guys I'll try recapping the dark one first just to be able to compare the 2 side by side again , I will also check the xstr sockets and pots ( without changing settings ) I am expirienced with electronics so no prob there. And keep an eye on the backwards cap !!!!!!! I have 2 of them to compare to each other so that will help

Later
Buzz

Anybody had any success using the stereo adaptor box from Urei ??? I have one but the units sounded SO different I never hooked it up

This manual has schematics for ALL of the various revs, and also has the adjustment/alignment procedures:

http://www.jblproservice.com/pdf/Vintage%20JBL-UREI%20Electr onics/UREI-1176LNmanual.pdf

Bri

Buzz · « **Reply #12 on:** May 08, 2006, 07:20:09 PM »

UNO MAS I have some op2134 op amps from a previous project anybody try these on the input stage ??? ( they are pin for pin compatable )

Mouser P/N's
Radial 100uf 25v 1ea , 647-upw1e101med
Axial 100uf 25v 3ea , 647-tvx1e101mad
22uf 25v 1ea , 647-tvx1e220mad
47uf 50v 4ea , 647-tvx1h470mad
68uf 63v 1 ea ( part in the unit is 16v ) 647-upw1j680mpd
470uf 550v 1 ea , 75-516d477m050pr6a
1000uf 50v 3ea , 75-53d50v1000

Later
BUzz

Buzz · « **Reply #13 on:** May 09, 2006, 04:20:51 PM »

So no feedback on the Tantalum caps or OP1234 IC ?????

LAter
BUzz

Wayne Kirkwood · « **Reply #14 on:** May 10, 2006, 11:09:00 AM »

I would replace the almost any tantalums with electrolytics to reduce distortion if they are coupling or emitter bypass caps. Tants aren't really a problem in supply decoupling, when low-leakage is required or in time-constant circuits. But (and this is a very big but) they are prone to short big-time particularly the dipped tants.

zmix · « **Reply #15 on:** May 10, 2006, 01:12:08 PM »

Tantalum can be fine when properly polarized, and they do not dry up like electrolytic caps do which is why they are used in timing circuits (the impedances are so high in the 1176 that the timing caps are 0.022uF film caps!!). If the input caps are not polarized, you should probably use a film cap, assuming fidelity is a concern (which begs the question - why use an 1176 if fidelity is a concern?)

In one of my 1176 I replaced the 1uF electrolytics with 2uF film caps. These were the only caps directly inline with the audio. (rev B 1176)

Buzz · « **Reply #16 on:** May 10, 2006, 02:08:16 PM »

Thank you very much guys I just want to make SURE I make the right changes on this unit !!! Jim from Audio Upgrades also answered my ?'s regarding the Tant's ( must have been a misprint on my manual's they show tant's ?????? ) so I'm using electro's .

Also I'm going to try the OPA2134 op-amps in some tests to see what the difference is

Again
Thanks guy's !!!!!!!!

Later
Buzz

I;ll post my results later maybe in a small clip ?

Buzz · « **Reply #17 on:** May 16, 2006, 04:54:42 AM »

OK so I replaced all the caps in the DARK unit it sounds brighter/better ( closer to the other unit ) but when going to calibrate the repaired unit I noticed the the sensitivity is about 7db lower ( I do have a BB 2134 op amp in it !! I tried it instead of the ne5532 )

when checking it at -10db ( sending the same signal to both units the recapped unit shows -7db relative to the old unit ???? )

I will stick the ne5532 back in tomorrow to se if that makes a difference ( the recapped unit is a rev H , the other unit is a rev K ) Urie removed r16 on the rev K unit no holes/pads I believe it was an offset pot for the 2 input op-amps ???

Does this make sense to anybody ?? or do you think there is something else wrong ?

LAter
Buzz

zmix · « **Reply #18 on:** May 16, 2006, 01:08:05 PM »

Please check all of your solder connections. If one of the coupling caps on the input ( c30 or c31 ) are disconnected you would experience a 6dB loss, likewise if one of the opamps was not socketed or soldered properly, this would producethe same result.

Buzz · « **Reply #19 on:** May 16, 2006, 01:42:12 PM »

Thanks Zmix I compared the 2 units last night and the Problem child had all of the Xstrs socketed and the op-amp !! It appears that this is an old problem and they tried to fix it before but never got there.

I will check all resistor values and caps for soldering and make some comparison resistance checks ( I used to be an electronics tech for 25 yrs so if I cant find it well I should shoot myself )

It is possible that the op2134 op-amp is causing it Dave Williams told me to put a 20pf cap across the 2nd input amp and I didnt have one so????

I'm going to try again today
Thanks for all the help guys I will get this sorted out

Later
Buzz

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Author Topic: 1176ln dark unit ? (Read 6361 times)