VC3 xlr input not working

[SeekerofRock]

I have a gold lettered version of the VC3 that I love to use for different instruments. Unfortunately, the XLR mic input stopped working recently. The rest of the unit works fine (I used it last as an input for bass guitar to the board) but I get nothing through the XLR now. I read in the manual that inserting 1/4″ disables the XLR mic jack so there are never two simultaneous inputs and wondering if something is not communicating to the 1/4″ jack when it is clear.

Any ideas on what the problem could be? I really like to use it for micing guitar amps.

Also, I just joined here, but have loved and used Ted Fletcher-designed products for almost 10 years now, including a VC1Qcs, the VC3, and an MQ3. I was reading about the VC3 in a thread below. I know there wasn’t a VC3Qcs made, but I thought the MQ3 was what that box was, basically a VC3Q with the new current sense pre design. I bought it paired with a JM47 mic which still sounds fantastic, too. Thank you for the enjoyment I’ve gotten from your wonderful designs and products!

[Ted Fletcher]

Thanks for your kind words….

Hmmm… yes, it could easily be the contact in the jack socket not making properly. You could try putting one very tiny squirt (very tiny!) of WD40 into the line-in socket and then pushing a jack plug in and out several times, that should clear it. If you continue to get problems, as a last resort I can fix it for you.

Yes you are right about the MQ3!

[SeekerofRock]

Firstly, thank you for the response, as I know you are a busy man.

I tried some DeOxit in the 1/4″ input jack, pushed a plug in and out of it several times, but still no XLR reading. When I opened up the box after I first noticed that it wasn’t working, the green grounding wire attaching one of the 3 pins to the metal case was not connected, so I had my guitar tech solder it back to the pin. That didn’t solved it either so I’m wondering what it may be that’s causing this. Is there anything else you could think of? I can post photos of the insides if that would help.

[Ted Fletcher]

It sounds like there’s a definite electronic fault. If you have a competent tech around, I can supply circuit information.

If you need me to fix it, the cost is £30 plus the cost of returning it to you, which is £4.50 in the UK; but it looks like you might be in the US so that would be a bit more. I don’t mind working on old Joemeek gear, but I do draw the line at studio consoles nowadays!

[SeekerofRock]

Thank you, Ted. I may take you up on that offer if you don’t mind, as I trust you more than anyone to get it going again. I’m going to take the cover off and check around with my unskilled eyes for anything obvious. If I can’t find anything, I will send it to you from Hollywood, FL, USA, zip 33020. Thank you again for your time in responding!

[SeekerofRock]

Well, I priced out what I believe it would cost to ship it to you and pay the repair cost and came up with about 50 pounds. The only tech I’ve used here where I am (besides my amp tech) charges 50 pounds just to look at something, then additional for parts and repair. 😥 If I could diagnose the problem and tell my amp tech what needs to be replaced, I’m sure he could do the soldering work.

So, how would one go about determining what the actual problem is (the xlr input not working)? It seems like it could be anything from a simple loose wiring connection to a faulty mic preamp chip to something in the input jack not registering that there is no cord plugged into it (just speculation…I know absolutely nothing about complex electronics). Any ideas or tests I could do to help determine what the problem could be?

[Ted Fletcher]

Do you get any sound at all through it when in the ‘mic’ condition? Are there any bad hums or crackles?

It’s unlikely to be a chip fault, more likely to be a capacitor fault…. the input has a pair of high voltage capacitors separating away the phantom power from the input chip. If one of those goes ‘soft’, then it can cause the input to stop working, but the line in would work OK. But that’s speculation….

If you want me to fix it, just send it to me at the Sound House.

[SeekerofRock]

I get absolutely nothing from the XLR now(and nothing on the input meter), and there was no crackling or humming that I remember before it went silent. Here are some photos of the inside if it helps, or I could take closeups of the caps if you tell me which ones could be the culprit.

I did notice when I first opened up the case that the case ground wire wasn’t attached to the pin, but would that cause the xlr input not to work?

[Ted Fletcher]

In the last picture, note the IC on the left hand side of the picture…. this is a SSM2017 mic preamp chip. To the left of it there are two large capacitors, they are 100 microfarad and with a working voltage of 63V. It’s most likely that one or both of these are faulty. They should be replaced with new. Most likely that will fix it, if not, then change the SSM2017 as well.

Dont forget that you need to cover up the light cell if you are trying to operate the VC3 with the top cover off! 😯

The ground being disconnected on the XLR would most likely cause severe hum and possibly also stop the phantom power from working.

[SeekerofRock]

I’m going to try to find these online and have my amp tech unsolder the old ones and solder in the new ones. He did this for a TASCAM cd burner I have (once I told him which cap needed replacement) and now it works perfectly. Thank you, sir, for all of your responses and help!

One more question if I may…as I mentioned previously, I also own a VC1Qcs and MQ3, and love them. In some older posts (shortly after he bought the name rights) Alan Hyatt kind of slammed the ‘cs’ version of the VC1Q on some online forums about the omission of the transformer in the preamp section and implied that the ‘cs’ version has a poorer quality preamp than it’s predecessors. Of course the change in the ‘cs’ was for a reason, be it cost or sound or both, but would you say there is a big difference in the quality of preamp in the VC1Qcs versus the VC1Q? I love the sound of my ‘cs’ (and that’s what counts), but Alan’s comments seem to have been carried on by readers and posters in other forums as a bit of an urban myth, even making it as far as descriptions on ebay, and I’m just wondering what your take on the different preamp changes in the VC1Q versus the ‘cs’ version are.

[SeekerofRock]

Ted Fletcher wrote:

To the left of it there are two large capacitors, they are 100 microfarad and with a working voltage of 63V. .

The ones I am planning to order are by Mallory and are 10mm diameter by 13 mm height (100uF and 63v of course). Will that size (ht. and diameter) work on the VC3 pcb? The guy that is going to do the work told me the exact physical dimensions of the replacement caps are important to get correct.

[Ted Fletcher]

Those caps sound fine.

About that time, when Alan was buying the JoeMeek trademark, there was considerable ill-feeling around; the business was not doing well mainly due to the horrors of 9/11 and Alan went into print with a number of outbursts that I’m sure he is not particularly proud of.

The truth about the CS input stage is that although under some conditions it is marginally less quiet than a regular SSM2017 input chip, it has some spectacular advantages; it is almost impossible to overload, and it is completely independent of the quality and length of the microphone cable. An added bonus is that it generally improves the sound of dynamic microphones. I introduced the CS input stage into all JM mic preamps for two reasons…. a) because there was a world shortage of SSM2017 chips, and b) because I genuinely prefer the sound of the CS circuit.

I’m not sure where the ‘transformer’ comments came from….. we only used input transformers on the very earliest VC1s, virtually all of the later ones were without transformers.

Nowadays I use input transformers and a modern version of the CS circuit working together.

So to put it all into perspective, The modern version of the SSM2017 makes a perfectly good mic amp but to my ears it sounds a little ‘brittle’ and I prefer either my own, or one of the more exotic amplifiers like a re-issued Neve.

There is absolutely nothing wrong with a CS amplifier and it is certainly not a ‘cheap’ solution.

[SeekerofRock]

I had my amp tech install the two new 100 uF 63v Sprague caps. I put it all back together and…….still no signal from the xlr jack. 😥

I probably should send it to you at this point if you don’t mind working on it. I think I can send it via USPS international flat rate shipping for a reasonable cost.

Send it to the address below, correct?

The Sound House,

Hunsdon Road,

Torquay,

TQ1 1QB

[Ted Fletcher]

Yes, that’s right. Just send it to me at the Sound House and I will fix it.

[SeekerofRock]

Thank you, Ted. It is on its way to you, sent out yesterday from Hollywood, Florida.

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