Reddish 500 EQ

[JMan]

Also id like to add that there may be a grounding issue. I was testing through my daw and I did not get any tone pass through more grounding noise. I tapped on the knobs it seems the freq knob is very microphonic. not sure if this helps any or if its just more in the way

Let's ignore this until we have the input transformer working. I'm fairly confident that if we can get signal passing and the circuit working as expected, this will go away, but we can always troubleshoot it later if it turns out to be a secondary problem.

 

[Forcemusicgroup]

standing by. Iron is heating up

 

[capacitorless]

Tapped on the knobs and microphonic. If I adjust the vr2 the grounding noise comes up in level (gain)

I meant tapping on the body of the relay in question, to see if it frees up mechanically

The MGB fuel pump needed a good thwack, applied directly to the body of the pump, to be effective. Not suggesting you take a hammer to it but a solid tap might do something useful. That's assuming the other stuff in progress is solved, of course.

 

[Forcemusicgroup]

I meant tapping on the body of the relay in question, to see if it frees up mechanically

Did this no change, one relay is closing much harder than the other. I can actually feel the relay closing.

 

[Forcemusicgroup]

Let's ignore this until we have the input transformer working. I'm fairly confident that if we can get signal passing and the circuit working as expected, this will go away, but we can always troubleshoot it later if it turns out to be a secondary problem.

Retouched the joints on the pcb, j1 pcbs (Really tight) But got it done. Also retouched the back for good measure. No change. In signal. Should I redo the test?

 

[JMan]

Did you also retouch the transformer pins 2 & 5? (and maybe 3 & 4 while we're at it?)

 

[JMan]

Did this no change, one relay is closing much harder than the other. I can actually feel the relay closing.

This is an interesting note even if it turns out that it's a red herring. Which relay closes "harder?"

 

[Forcemusicgroup]

The board

This is an interesting note even if it turns out that it's a red herring. Which relay closes "harder?"

K1, when I hit engage, K1 really kicks. standing by for next steps

 

[JMan]

standing by for next steps

Did you also retouch the transformer pins 2 & 5? (and maybe 3 & 4 while we're at it?)

Still not sure whether you did this

 

[Forcemusicgroup]

Still not sure whether you did this

I have. did them all.

 

[capacitorless]

I wouldn't expect a relay of this size to engage that obviously. It sure seems like there's a potential mechanical problem in K1. As JMan is saying, however, solving one thing at a time is the way of Zen (or something like that).

 

[JMan]

I have. did them all.

Okay, let's repeat the tests in post #469.

When you do tests 3 & 4, make sure you measure between the pad marked "Or" (from left to right, the third pad of the output transformer leads) and "Out +" on the edge connector. I was a little confused by your report the first time around - I think you were measuring from a different spot.

 

[JMan]

I've gotta go get some sleep. I'll check back tomorrow to see what the results of the re-test are.

 

[Forcemusicgroup]

This might be a simple issue of the meter not getting a good solid read. My Fluke 179 does this sometimes if I'm holding it against solder rather than the metal lead or an exposed bit of pad, or if there is any shakiness or wobble on the end of the probe (even barely perceptible - you'd be surprised how little play is required for the meter to get weird). However, let's leave this alone for now, because as you'll read below, it looks like we may have found our issue.

Okay, this would suggest that we have no short to ground, which is good, but also leaves us back at square one.

This is different than before. In previous tests, you said you had AC signal on the primary side of the transformer when injecting a test tone with the unit set to "IN." Now you do not? EDIT: Ah, I see that in this post you took the AC measurement at the card connector - I misunderstood and thought that you confirmed that you had the same signal on the primary of the transformer. So you probably didn't have it then either.

If that's true, then @capacitorless is right, the issue is on K1. Let's test both of the relays. Perform the following tests to confirm, after which (assuming these come out as I expect) we will probably just need to replace one or both of the relays:

Test 1:
-Power ON
-EQ BYPASSED
-Send test tone
-What AC voltage do you measure between In+ and In-?
-What AC voltage do you measure between Out+ and Out-?

Test 2:
-Power ON
-EQ IN
-Send test tone
-What AC voltage do you measure between In+ and In-? (It's fine if it's identical to the measurement from above)
-What AC voltage do you measure on the J1 connector between the second and third pins from the right?
-If you had voltage on those pins of J1, do you read the same voltage between Pins 2 & 5 of the transformer?

These first two tests should confirm whether we have a breakdown on K1. Now let's double check K2:

Test 3:
-Power ON
-EQ BYPASSED
-Do you measure continuity between "Or" pad of Output Transformer leads and "Out +" on edge connector?

Test 4:
-Power ON
-EQ IN
-Same question as in Test 3

Continuity on the Pad "OR" on T1 for eq in, and bypassed when not engaged. My meter tells me voltage is passing though(beeping), engaged. I have long tone (solid) tone.

 

[capacitorless]

Just to be clear, you mean when it's beeping, there's continuity? In other words, you mean that the meter is providing the voltage you're talking about? I usually say that there's a voltage present when there is an actual voltage being measured (whereas a continuity test is simple "there is continuity"). Not busting your chops on wording, just want to be clear.

I too need some shuteye but it seems like progress is being made. That relay being funky doesn't seem normal and I'm particularly curious about that, even if ultimately isn't the source of the problem.

Thank you for doing all these tests in real time and responding quickly - it's so much easier and fun to help out when you do

 

[Forcemusicgroup]

Thank you both for the help. I really appreciate it. Especially when we have lives. It can get tricky. However I am absolutely loving the EQ thats working. So many uses for this tool. I do have a pair of AM 25 and Chamboard 250 EQ's I love but this EQ is just the sweetener. Waiting to try these out in M/S. just to see its usefulness.



So when there's voltage in the circuit(showing continuity ). It will beep. When it's regular continuity it gives me the long tone.

However Have a great night guys, I'll close down shop and start again tomorrow. Anyone do zoom? im sure it can get figured out fairly quick that way.

 

[capacitorless]

That's super interesting! I need to think this through fresh, but I wonder if the relay is horked enough to be passing some/all of the 24v actuating voltage through a pin that it shouldn't (eg one or more of the DPDT pins). When you get back to things, see if you can measure the voltage that it is indicating.

I need a meter like that. Very cool. (edit: please post the make/model when you get the chance!)

Zoom would be good here but I would defer to JMan first as I don't have one built yet to compare to (and I have pretty full days through the weekend)

 

[capacitorless]

To be more specific, with power applied and eq engaged, and nothing plugged into In+/In- and Out+/Out-, measure for voltage between the following pins:

pin 8 on K1 and pin 5 on the card connector
pin 9 on K1 and pin 5 on the card connector
pin 8 on K1 and pin 13 on the card connector
pin 9 on K1 and pin 13 on the card connector

This is checking for DC vs both grounds (audio & power) on two of the 6 pins of the DPDT part of the relay. There shouldn't be any.

I'm not 100% how the grounds are connected in the 500 chassis, which is why I'd check both.

For completeness I'd check all 8 pins against the grounds just to be sure things are cool (16vdc on pin 1, -8vdc on pin 16, 0vdc on the rest), and do the same with K2.

 

[JMan]

Continuity on the Pad "OR" on T1 for eq in, and bypassed when not engaged. My meter tells me voltage is passing though(beeping), engaged. I have long tone (solid) tone.

Just to avoid confusion, the output transformer is T2.

So, when the relay is engaged (Unit IN), we expect lead 4 of T2 ("Or" pad - I believe this is the yellow lead if you used the UTM output tranny) to be connected to "Out +" on the edge connector. When the relay is disengaged (Unit BYP), the connection should be broken. I've read what you wrote a couple times and I'm not clear on whether this is the case or not - probably just an issue of reading comprehension, I am pretty sleep deprived these days.

Did you redo Tests 1 & 2 from post #469? I only see the report of redoing Tests 3 & 4. We need to do the first two as well to see if touching up those solder joints made a difference.