[BUILD] CAPI 553F~500 Series~LC Equalizer~Official Support Thread

[jsteiger]

No don't pull it yet. It was just a thought. I'll get back to you hopefully tomorrow with test points thru the circuit.

 

[Mishegas]

Thanks so much Jeff!

Please get some sleep!

 

[jsteiger]

You did say it was A2 getting hot right?

Measure DCR from gold finger #2 to gold finger #5. It should read open with no measurable resistance.

 

[Mishegas]

Yes A2....and more specifically it's the MJE172 (reddot) and the BD140 (gar2520) that are really hot.

According to Fluke

PIN#2  to PIN#4 = 24.8 ohms
PIN#2  to PIN#5 = OL (open)
PIN#1  to PIN#5 - 10 ohms

 

[jsteiger]

OK this is all good.

I will dig in tomorrow and work on the test points.

 

[Mishegas]

Thanks  so much, Jeff

I've got some family/holiday stuff starting tomorrow so no rush. I really won't be back at the bench in earnest until Sunday. I'll be darned if I can't stop thinking about it though!

 

[jsteiger]

I have just added a Test Points pdf to the first post of this thread at the bottom of all the support doc downloads.

 

[michaeltgatto]

This site helped me figure out capacitor values.

http://www.electronics2000.co.uk/calc/capacitor-code-calculator.php

 

[Mishegas]

Hey Jeff,

First, thanks for the test points PDF....

Second, I hooked the 553F to the jig w/ test tone and started probing...

#1 600mV
#2 600mV
#3 ...here's where my continuing 553F nightmare gets a little worse - ( I'm still a bit groggy from a red-eye flight last night...shoulda waited til tomorrow...) - I managed to fry something while probing + on C19 - I think the probe hit a resistor on the A3 follower... heard a little *tic* and smelled that smell. In any case the Fluke started @ 14V and ranges down to 1.1V. God knows what blew? no sign of a frying....?

needless to say I tested thru to #5... same deal as #3

I pulled A3 and A4, which *looked* ok, pulled & tested the 5087 and TIS97 from A3 which didn't show any shorts on a Peak Atlas (as well as pulling and testing c19 which came up fine)

Thought I'd post B4 I bust out another puck of solderwick...

I'm open to ANY suggestions....

OY!

 

[sharpeleven]

Just finished building two of these beauties! Great sounding EQs!

Everything works and sounds as expected EXCEPT that one of the units has a considerably lower output than it should (a difference of 19.3dB when measured from the DAW compared to the other). With a 4dBu (*) 400Hz sine wave  at the input the unit in question will only put out 0.134V.

Here the actual test point values:
TP1: 600 mV
TP2: 600 mV
TP3: 597 mV
TP4: 594 mV
TP5: 591 mV
TP6: 241 mV
TP7: 403 mV

here are Jeffs published target values:
600mV (after A1 receiver)
600mV (after HPF PCB)
596mV (after A3 follower)
594mV (after LPF PCB)
591mV (after A4 follower)
243mV (before A2)
413mV (after A2)

So it all seems very much in the zone, with TP7 being just 10mV lower than Jeffs on this unit. Not sure if that would account for the significant loss of signal? If no, wouldn't the only possible fault be somewhere around the output transformer? Maybe I have a faulty transformer? Any advice is highly appreciated!

Everything else works great, no noise, boost/cut identical to the other unit, sounds just a good as the other correctly working unit, just a lot softer at the output. I've triple and quadruple checked all wiring at the transformer and all looks correct. I did sucessfully calibrate the unit according to the instructions.

(*) actually 2.219V, which is as close as I can get my plugin based signal generator to output 4dBu (should be 2.227V)...

 

[jsteiger]

Sharpeleven, scroll back a few posts and you will see some tips on how to check the 2503.

 

[sharpeleven]

Can you desolder all of the leads for the 2503 and measure the DCR of each winding? Set your DMM to a range of less then 100 ohms.

That would be:
red to brown
orange to yellow
green to blue
violet to gray

red to brown: 8.4 Ω
orange to yellow: 8.3 Ω
green to blue. 8.3 Ω
violet to gray 8.3 Ω

thanks!!

 

[jsteiger]

Those are right so far. Measure from one lead from each winding to the other windings to make sure there are no internal shorts anywhere. The only combinations that should have measurable DCR are the winding pairs in the quote you copied.

BTW, have you tried swapping rack slots and checking all cabling and convertor settings?

 

[sharpeleven]

Thanks for your help, Jeff!

Yes, equal conditions for both units as I'm just swapping them using one of your jigs here at the bench.

Following your directions I do measure the following additional resistances:

yellow to violet: 8.4 Ω
grey to orange: 8.4 Ω
grey to yellow: 16,7 Ω

 

[jsteiger]

Well, the best thing is to start from scratch measuring DCR of the 2503. The 16.7 ohms could mean something is shorted or 2 other leads were touching.

So, measure each and every lead to all other leads and write down the results. Make sure that none of the leads are touching each other. Only report back with any color combos that have resistance.

 

[sharpeleven]

ok, latest results are in confirming prior measurements. I checked again all possible combinations as you requested, same procedure as first time. It's a pretty straight forward operation, so I'm pretty confident we can rule out any user error on my side. Sure never hurts though to think twice before sending iron across the atlantic... 

I actually found one additional resistance between orange & violet (of just 0.01 Ω) that I must have missed the first time. Prob. meaningless - just mentioning it for sake of completeness.

List of all measurable resistances:
brown - red: 8.3 Ω
orange - yellow: 8.3 Ω
orange - violet: 0.01 Ω
orange - grey: 8.3 Ω
green - blue: 8.3 Ω
violet - grey: 8.3 Ω
violet - yellow: 8.3 Ω
yellow - grey: 16.7 Ω

all other combinations do not produce any measurable resistance.
thanks!

 

[jsteiger]

Well there is the problem. Orange and violet are shorted internally causing the 16.7 reading from yellow to grey. None should have measured 16.7 since that indicates 2 windings in series. That told me that either two other leads were touching during that measurement or there was an internal short. I did not doubt your abilities 

Can you email me with your real name and I'll send you a 2503 today. jsteiger1965 at yahoo

Glad we found it and sorry for the trouble  :-[

 

[sharpeleven]

Thanks for your effort and time! Will email you shortly...

No offense taken anywhere whatsoever - I'm a complete noob and know nothing, trust me! ;D  just trying to be verbose enough to try'n compensate for my complete lack of precise tech-lingo and help the process to best of my abilities. Hope I didn't waste anyone's time by taking up all that bandwith.  8)

 

[Mishegas]

Greetings!

Whatever the hell I shorted while probing the test points seems to have led to a solution to my previous problem (for quick reference, my 553F was NOT passing audio as well as overheating the A2 DOA)

I pulled both discrete followers, pulled all DF components, resisitors and caps tested fine, BOTH 2N5087's were fried, as well as a TIS97* being shorted, so I replaced ALL transistors in both DF's and put it all back together, clamped on the test jig, and *bingo*! Passing audio! And no roasting OpAmps!

Not being in possession of a proper schematic- I'm incredibly curious if the DF transistors could have been causing THAT much mayhem?

Anyhow, I haven't hooked up the sig gen and shot a 400hz through it yet....but I'm feeling somewhat lucky that this somehow (and apparently inadvertently) solved this problem! However I'm also a bit upset that I really can't be sure what the initial problem was!, and exactly what fixed it?...(again, I haven't tested/calibrated yet...)

*my girlfreind's minimoog is FULL of 'em! 

 

[kante1603]

Slaughtering a minimoog..........you sir are a monster.....
Glad the issue is solved.

Udo.