Tech Mecca: Pendulum Audio Authorized Service Repair

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Pendulum Audio authorized service/repair

Tech Mecca is the authorized service and repair provider for Pendulum Audio products.

Located in Carmel, NY 10512 - roughly 60 miles drive North from New York City
Tech Mecca is not a retail or walk-in shop. All work has to be scheduled in advance.

notes from John Klett / Tech Mecca Inc.

I service Pendulum Audio products. Service repair work has to be scheduled in advance. I do other things including travel work and I even take vacations from time to time so my availability is off and on. I don't take in other products for general service/repair and if you want to read more about that you can go HERE. I can't provide any schematics for Pendulum Audio products - would if I could but I can't (NDA). I may offer some email help and post some info here because things like broken off knobs and controls, aged out tubes, dead meter lamps, and some of the basic alignment items are things that users or their local techs should be able to handle without shipping units to me.

If you are thinking of sending your Pendulum Audio gear in for service just send an email with some basic info HERE

NOTE: My availability for the rest of 2024 is going to be extremely limited to non-existent.

Normally I go off to do some travel work, or we grab some vacation time, and that will take me away for a couple weeks... but this time it's going to be longer. Some of this is just the upcoming holidays but this year we add packing up a house and moving - not our primary home or my shop - but still - this is going to eat up the rest of this year and a little bit in to January...

Quicktakes

Gain Stage Tubes used in Pendulum tube studio gear (MDP-1, OCL-2., Quartet, and Quartet II) ... the tube gain stages in these units each use one 12AX7A/ECC83 and one 6922/ECC88. Pendulum used 12AX7 tubes from Ruby Tubes which you can find current versions of at rubytubes.com - I am not sure which current version from Ruby today is closest to those used in Pendulum back when these units were manufactured - there has been some variation over time. One can also search for Shuguang 12AX7 tubes which seem to be where Ruby tubes originate (not dead certain about this but seems to me to be the case). After sampling many of the tubes in current manufacture I settled on using a Russian made Mullard reissue 12AX7A/ECC83 - these have taller plates and tend to be quieter and lower distortion. There is also a Tung Sol reissue that is very similar and tests fine but I am still working my way through the Mullards that I bought in bulk. The original 6922 Pendulum used was a Philips ECG JAN 6922 military spec tube (Joint Army Navy) and these are still easy to find NOS from reputable sellers. I had these in stock for a long time but the cost has climbed up and the reject rate went up as well so now I use new Russian-made Electro Harmonix EH 6922/ECC88 tubes which are consistently good with a low (<20%) reject rate... that is what I buy and use... that said I test every tube a number of ways including testing them in whatever unit I am servicing and I reject some percentage of these tubes at various points in the process. Tubes are not precision devices. Some can come out of the box, go through testing and work great in whatever unit they are in for a month and then poop out, others get culled before they get plugged in to anything, others go in and run for decades. last note is that many many 12AX7 type tubes are oriented to guitar amp use and these tend to be "hot" and have some color... great for guitar amps where you may want some color but these will not make spec in Pendulum gear. I have used rejects from Pendulum repair work in guitar amps where that color (low order harmonic distortion) is musically useful.

Remote Cutoff Tubes used in Pendulum tube studio gear (6386, ES-8, Quartet II) ... remote cutoff tubes have a special grid construction where the grid wires are closer together at the two ends and spread apart in the middle. By changing the bias of the grid more negative the open spaces between the grid wires at the ends 'close off' sooner, effectively reducing plate area as seen by electrons boiling off the cathode... this changes the gain of the tube. Pendulum used NOS GE 5-Star 6386 tubes (with '6386' etched into the glass) in the Pendulum 6386 limiter and used 6ES8/ECC189 tubes in the Pendulum ES-8 and Quartet II. 6386 and ES-8 tubes have different pinouts. I have seen some units come in with 6386 tubes where I would expect to see an ES-8 and these had been converted from the ES-8 pinout to conform to the 6386 pinout... and there are some resistor values that change... apparently Greg at Pendulum did these for some customers. Replacement tubes... JJ tubes make a new 6386 tube which I have tried... they certainly work, however I have mixed opinions. They work fine in my own vintage gear but I turn that equipment off when not in use and I am not in the studio anywhere near as much as I would like to be so... inconclusive. The JJ 6386 costs around $165 and some fellow techs who have used these in various vintage gear, some using eight of these things in one dual/stereo unit, have expressed some sadness at how long they last before fading. The original RCA ones may have run in spec for decades while early reports are that the new ones go a year or two before emission falls and performance drifts off spec enough to warrant replacement... 'they start off hot and fade off faster than one would like'. I have seen NOS 6386 tubes available from reputable vendors for as low as $250... but the whole NOS tube scene is pretty frustrating as there is a considerable incentive on the seller side to do bad things like "flashing" the heaters in used tubes to perk up the cathode emission, maybe they re-print the tubes to make them look new, and sell them as NOS... these can fade out pretty quickly and you are back where you started. 6ES8/ECC189 tubes are only available as new old stock. They are relatively cheap - going anywhere from $10 to $50 each. I buy these in bulk and I often set aside well over half of them... so the remote cutoff tube "thing" is a bit frustrating. When you change these tubes you need to do an alignment procedure that sets the gain and balances out the two triodes in these tubes - this procedure is the same for both 6386 and 6ES8 tubes in Pendulum units... HERE

Meter lamps used on older pendulum gear are incandescent bulbs that burn out - Pendulum note HERE - the original 6x24mm Festoon lamps are AC122 type 12V, 1.2Watt. There is also a higher voltage (24-26V) lamp that is dimmer (because it's running on half its rated voltage) but lasts a lot longer called an AC360... both of these plus the Sifam AL29 meters are available at IMS. When I have units in for service I offer up an LED conversion which involves making a little sculpture with some LED's and a resistor that I solder in where the old Festoon bulb went... at some point I may make a video of that... but don't hold your breath.

SPS-1 acoustic guitar preamps are solid state (not tubes) - there are some normal issues common to most gear as it ages... some switches and controls wear out, not too many component issues, however a number of SPS-1 units have come in with physical damage and those were problematic... not that they couldn't be repaired... it's more about finding a few key parts ... I have them now but... costly ... comment below.

These units rack mount and you would think that they would be safer in a road rack... that's what I used to think. SPS-1 and HZ10 units are one rack space (1-3/4") and have some depth in the rack (SPS-1 more so) - the front panel also serves as the rack "ears". The leverage the weight toward the back of the unit has over the front panel means the when the back bounces up and down, even a little, there will be some flexing and stress on the wire "legs" of the controls that are directly attached to both the front panel and the large pcb inside the unit. Over time the metal fatigues and the wire terminals crack and break - causing intermittent noises, loss of function (like a band of the EQ not working right or changing intermittently), possible load clicks and bangs. Sometimes this takes a long time - other times the whole back of the unit starts to separate from the front panel and many controls are damaged, needing replacement, after one bad drop. Some of these controls are not stocked at distributors where they are available in small quantities - so I have those parts "built to order" (BTO) ... IF you rack mount these and other single rack unit items in a road rack that travels they need to be supported in the rack to prevent the back end of whatever it is from moving.

IF you have an SPS-1 or HZ10 with a lot of intermittent cutting in and out, bangs and pops, EQ sections sounding weird or some controls not doing what you expect - it's repairable but it could be a costly repair - mostly due to cost of BTO controls.

HZ10 and HZ10SE units are not as deep in the rack and weigh less ... and the controls are a different series and cost less so... the flex problem does happen in HZ units but not as much it seems ... and the controls are available so don't have to resort to high cost semi-custom parts

more content will be added - just getting this Pendulum specific chunk of my site going... long overdue...