1176 in 51x/500 format, or 51X-F76 Build Support Thread

I found this little site which really helped for converting between Vrms and dbU and other units. 

http://www.sengpielaudio.com/calculator-db-volt.htm

what sockets did you use for opamps? the ones from CAPI are slightly too big [pins are ok]

Hi.

According to the BOM, from Farnell the P/N

PINS/SOCKETS FOR DOA:
149318, 149319, 1336236, 1336237

I finished mine up this weekend, just need to fire em up, calibrate and test 'em. FINALLY!

The Gimmer

@audioGlimmer, if you don't care about the visuals, aside from checking the voltage on Igor's Input Amp, the other calibration steps are for the meter display only.  So, if you don't care about that, you can go ahead and run audio thru it!!

Finished my 2 F76s. The results so far:

Unit 1 perfect.
Adjusted Igors input amp, and all other voltages checked out fine.
Calibration procedure is very clear and worked perfectly. Used external signal generator and hardware VUs for bias, GR and led 0VU calibration, v easy and used s/w scope for distortion adjust. [Actually you could do that almost by ear with 1KHz tone and good monitors, listen for 1st harmonics minimum level]

Unit 2 issues:
Hmm. Voltages all check out fine, adjusted input amp all good. However, the LED meters are not working. On GR the topmost LED is lit [as it was on first unit so probably fine but needs to be adjusted to display 0 gr correctly] but on level the LEDs are not working properly. Occasionally they flicker up and down, otherwise stuck on red LED  only. Its not the TL074 or the LM3916 I checked the chips in the working unit. Out of time today so I'll check the board over during the week. maybe a cold joint in the LED section. The unit was passing audio I think so I suspect its just the metering section.

The unit that is working sounds fantastic. Thanks Igor, excellent work. My lunch box is now sadly full  :-\
2x API 512C
2 F76s
Mixbuzz 500
Fantastic portable recording treats!

The Gimmer

I had the same issue on one of mine.  I just had to keep messing around with the GR_SCALE trimmer before it worked right.  On mine, if I had that trimmer cranked too far in one direction, the LED meter would literally display in reverse. 

I'm in a bit of a holding pattern for my build right now. . . for the zobel network in the LL1524 output transformer, I'm using 4n7 WIMA capacitor and 460R resistor.  As I understanding it, higher value resistor and lower value capacitor will induce less treble roll-off.  Igor concurred that these were the values he utilized on his builds.  I will have to wait for parts to arrive from Mouser, but for now. . .

back to the attack/release/ratio board.  Capacitors will be found in this baggie.







Next, I assemble the interconnect cable for the attack/release/ratio board.



The trick here is to always be aware of pin 1's position and to make sure the red-marked cable corresponds to pin 1.  The PCB is marked for pin 1.





I used a C-clamp to seat the press-fit cable ends.









After double checking the proper cable positioning and pins are in the correct locations via multimeter, solder the cable to the attack/release/ratio PCB.





Next, I locate the Grayhill switch stop pins and retaining stickers.  Watch out. .  . they're tiny.  Now is no time to let things roll off the table.



Per the documentation on the front end of this thread, insert the pins into position.



It should look something like this when all the pins are in.



And, place the retainer stickers to set the pins.



Attack/release/ratio board is now complete.

Next, I decided to do the main PCB resistors.  Note, because I'm building with the IC line receiver, I do not install R5' 270R.





And the the main PCB capacitors







Next up were the IC sockets, trimmer pots, and relays.





And, more capacitors. . . watch out for polarity on these guys.



This cap did not have any polarity indication except for the long leg (+).



The + side of these little guys are indicated by markings. . .



Make sure they correspond to the markings on the PCB when installing.



And, capacitors are in.







I purchased a pair of salvaged LL1524 output transformers from Igor's friend, and they were shipped with my kits. . . they probably didn't know which ones were going in for photo shoot  ;D  There are a few dings on them, but hopefully they have been tested electronically and passed muster.



I don't think it's completely necessary, but I put a couple strips of electrical tape here.



And soldered the transformer in.





And, that's where the project stands. . . just one resistor and one capacitor left for the zobel network, and I can do final assembly and calibration.  I borrowed a scope and a signal generator from a friend, so I'll have to learn how to use those funny tools in short order.

lookin' good.  Be aware when you wire your Input/Output pots that they're reversed on the pcb compared to the faceplate. 

mulletchuck said:

I just wanted to point out to anyone who recently bought this kit.  DO NOT throw out the unlabeled parts of the PCB that are in this picture: 

They're spacers for when you mount your transformer.    I didn't know this, and they are somewhere in a New York State garbage dump or recycling facility because they weren't labeled or explained.

Click to expand...

Thought I'd just quote this to remind others who might be following this thread. No need to insulate the trannys if you remember to space them off the board with these...

The Gimmer

One of my kits had the spacers (complete PCB), and one of them did not (pre-cut PCB).  I figured I'd build to the "worst case" scenario.  The tape solution is redundant as the metal casing does not come close to contacting anything. . . furthermore, the factory put a plastic film over the transformer covering critical areas.  This arrangement should be solid for the long haul.

you don't need those spaces if you use the LL1524s.  cuz those spacers would prevent the pins from touching the PCB.

UPDATE

Unit 2 fixed, calibrated and working perfectly.
The issue with the meters turned out to be a broken switch. I took the boards apart, had a real good look for any cold solder joints or other problems. [I knew the chips were good as I had swopped them in a good unit and they worked fine.] I worked through the meter section following the schematic. All components were correct, resistor values, caps etc and I checked the diodes were OK too. Hmm Surely couldnt be the switch could it?
Yup. Only intermittent connectivity in either position. Looked closely and switch looked slightly undone. Gave it a little prod and BAM:


So, need to fit a replacement switch.
I didn't have the correct size one to hand, and since I wanted to finish up calibrating the unit and actually USE it, I cludged an off board temp solution with some thin wires thru the front panel and an old DPDT switch I found lying about.

You can see the wiring and switch here:


These units sound fantastic, I'm very very pleased with them.

The Gimmer

I am building the F76 from naked PCB and so I am hunting for parts right now.

I chose to go with the balanced line receiver, all three Grayhills, the IJ Input amp and the IC output amp. Unfortunately I can´t find the 2N4249 (T1 in IJ amp) and the 2N4250A (Q14 in IC out amp). I just guessed now that a BC560 would do. What do you guys think?

And what´s your favourite source for the Lundahl LL1524 in Europe?

@ chunger :

AWESOME pictures!!! Really, amazed by your photo skills.

901: pn2484, pn4250 are the same transistors just in plastic. Or, pn4249.

LL1524: I bought them from andre tchmil

andre tchmil said:

@ andre tchmil do you have 2 1524 output trannies available still? I'd take 'em


sure how many kilograms do you need ?  ;D

email me for ordering, thanks

Click to expand...

Thanks for the info! I was already quite desperate on the transistors. But now I can even get it on Mouser. BTW if anyones interested I´d be happy to share my Mouser parts list once my unit is complete and working and I know I selected the right parts...

The Belgian cycling hero already sold me a chunk of Swedish metal and after desoldering it using American tools from the remainder of its previous home it fitted well with the PCB from Isreal. I´m in Germany fwiw. Globalization can be a good thing actually!  8)

Just wanted to let you guys know: I have finished mine after all!

There are a few things I had hassles with and maybe this info is of good use for others as well.

- as stated earlier I had difficulties sourcing 2N4249 and 2N4250A. I managed to get my hands on two 2N4248 though. The BOM mentions these as the primary parts to get with the PNxxxx types as exchangle. The 2Nxxxx have metal housing, th PNxxxx are plastic. I would like to advise heavily AGAINST the 2N types since they all so easily touch other parts on the heavily stuffed DOAs and cause shorts! And they are larger, too.

- The LEDs don´t line up well with the cut-out in the metal bracket and front causing a little tension on the motherboard. If I had to do it again I would try to place them not so tight against the board so that the pins get gently bent rather than the board itself.

- The Attack and Ratio Grayhills didn´t expose enough shaft for the knobs that I chose. Fortunately I could mill away a millimeter from the metal knobs. If you can´t do that pay attention to the dimensions when choosing knobs.

- For some reason I had difficulties to get buttons for the push switches. I´m currently using an interim solution by abusing the heads of two M4 hex screws. I think it´s funny...  8)

After adjusting everything I just toyed around with it a little and this thing is really fun! Even if my points from above may sound like trouble, it was fun to build and absolutely worth the effort.

Unfortunately I have never used a real Urei 1176, so I cannot compare. But I don´t care for originality. I think Igor made an excellent job on this one!

lookin' nice, dude!

Nice job.

- The Attack and Ratio Grayhills didn´t expose enough shaft for the knobs that I chose. Fortunately I could mill away a millimeter from the metal knobs. If you can´t do that pay attention to the dimensions when choosing knobs.

Click to expand...

I'm using same Kilo knobs, bigger ones tough, yes you need to trim the bottom, but i was aware of that, but needed bigger knobs,
feels better when turning those grayhills...

Allright Done Deal, had some weird things on this one, and i was kind of slow at troubleshooting, had been a while since last DIY.
First error was one my side and nothing that you'll encounter, had done myself a double sided home etched board like the Rackit,
for feeding both rails with one Supply, and audio on board etc.. one of the connections was not made properly so...

Second error, i had one resistor on the ratio Control wrong, and i was lossing signal when inserting the control Board.

Anyway Thanks Mr kapelevich.

I went all original, attenuator, Tranny, Amp etc....

Nice job Zayance, looks great with those knobs. Which Kilo ones are they?

I went T Pad & transformer input too. Did you use Igor's DOA [ the one that's like an eye test to build! ]

Incidentally Igor, nice touch with the metering, very nice ballistics. I also like the way in GR mode the very bottom LED is half lit to show you are in GR mode.


The Gimmer