maybe my mf-104z has problems?

[iksrazal]

Hi all,

I've had my delay for a few years though I haven't used it for a few months. I remember it working fine. I just got a new RME and xtramix and I tried hooking it up to the delay.

The problem is I only get the clean signal from AUDIO IN with EXT on, tweaking the knobs changes nothing. With INT on, I get only that INT sound (same sound with a signal in and no signal in, like feedback) but with a noticeable delay that changes when switching from short to long. With a signal in and INT on, I get the clean signal and the same INT delayed feedback sound coming out of MIX out, which doesn't change when the MIX knob is turned - the MIX knob seems to have no impact. I can't get the signal in to have delay on it no matter what I try.

The problem is I'm in Brazil and its a terrible place to send gear to and from the states. I do know electronics pretty well. Any ideas?

[iksrazal]

Spent more time with it today. There is a continuous squelch coming out of MIX OUT or DELAY OUT when in INT.LOOP, with or without a AUDIO IN signal, that I cannot remove with knob tweaking. Any AUDIO IN signal seems dry out of MIX OUT or DELAY OUT. I tried moving the daughterboard pins a bit and putting electrical tape over them, but that did not help. Any ideas?

The unit is over one year old and out of warranty, but I tried emailing Moog tech support with my problem.

[iksrazal]

I ended up calling Moog support, and was told the unit was self-oscillating in INT.LOOP in an unusual way. Excellent fellow and I appreciated the time he spent helping me.

With a Voltmeter on my side , we confirmed several voltages. No obvious problem. I could send it to a service center in Brazil, but I decided that I'll send it to the USA factory on my next trip to the states - I want to play it safe so I have a working unit again someday!

[phish729]

I suggest that if you are going to send it to the factory to get it fixed, just get the factory modification spill over feature for the extra 80 dollars.

I had a problem with my MF104z and sent it to the factory to get fixed and figured I would just take care of the factory mod cause its a neat feature.

[EricK]

There is another issue with the 104z, and that is that sometimes it will intermittantly fail to self-oscillate. Sometimes 4 repeats max at everything full volume and feedback maxed out. There is a permanent fix for this, and mine has it installed, yet it managed to fail again when I fired it up after a few months of not being used.

Eric

[Rabalder]

Sometimes 4 repeats max at everything full volume and feedback maxed out.

Same here. Its a very moody little unit.
I kinda like it..

Life is like a box of... mf104's.. You never know what youre gonna get.

[joe_moog]

There is another issue with the 104z, and that is that sometimes it will intermittantly fail to self-oscillate. Sometimes 4 repeats max at everything full volume and feedback maxed out. There is a permanent fix for this, and mine has it installed, yet it managed to fail again when I fired it up after a few months of not being used.

Eric

Hmm...mine just started doing this same thing, actually.

[EricK]

It is an intermittent problem with the 104z. It will self-oscillate at about 3:00 (or 8 on the panel markings) and it should do this indefinitely. Closer to 10 and it will build up with increasing amplitude. This is normal.

Sometimes though, upon applying power, one might get only 4 repeats max. Or it may be at a very low volume. Or it may suddenly fail to self-oscillate and then return to normal without warning or by reapplying the power.

I sent mine in twice and the first time they installed a resistor on the output buffer. The second time they installed a protection diode.

I was told the other day that they tested this with kilovolts and it did not fail, but I was not told what was causing the voltage spike.

So theres still something going on with the 104z, as I was told that my unit has the "permanent fix" which would have to be the protection diodes.


Now, other forum members have claimed that there is a jumper that is touching the chassis that is causing a short to ground that results in the unit failing to self-oscillate. A fix for this will require sliding a piece of a card or something between the jumper and the chassis. I don't know if this is valid or not honestly. See, the jumper is on a daughter board, which is hot glued to the main pcb. the hypothesis was that heat from the unit causes the glue to expand, which causes the jumper to short out on the chassis, but mine will do this upon powerup.

My little-to-nothing knowledge of electronics led me to look up a protection diode and what the page said that they do is to protect against voltage spikes.
I'll bet that there is some sort of voltage spike that is occuring with the power supply or in relation to the bypass switch, because sometimes my problem occured when I depressed the switch and was temporarily solved by unplugging and reattatching the power supply, sometimes multple times.

The sad part about it is that the 104 series pedals are some of the best delays out there and I was about to sell mine when I heard they discontinued the 104z. Perhaps the shortage of BBD chips wasn't the sole reason for it's DC.

Another factor that added to the intermittent problem is the fact that I sometimes go for a few months without playing because thats just how my creative juices flow (and my school schedule operates).

Eric