EH pulsar tremolo,why 78l09?

alexradium · Post by **alexradium** » 31 Jul 2020, 05:32

I got this big box 3 knobs pulsar tremolo,on the box it's written 9vdc 100mA,ok, fine,but inside there was a 78l09 regulator between the DC Jack and the circuit,where also the 9v battery connects.
Does it mean that EH power supplies were supposed to be 12v,or maybe 10 unregulated?
Because it's clear that feeding 9v in that regulator won't work properly.
Thanks.

JiM · Post by **JiM** » 31 Jul 2020, 06:51

Their main power supply puts out 9.6V :
https://shop.ehx.com/item/eu9.6dc-200/g ... es-europe/
(there are others 9.0V, but with a minijack connector for older BigMuffs)

Maybe this is a way to "encourage" customers to buy their power supplies instead of a generic one.

rockola · Post by **rockola** » 31 Jul 2020, 10:59

JiM wrote: ↑31 Jul 2020, 06:51 Their main power supply puts out 9.6V :
https://shop.ehx.com/item/eu9.6dc-200/g ... es-europe/
(there are others 9.0V, but with a minijack connector for older BigMuffs)

Maybe this is a way to "encourage" customers to buy their power supplies instead of a generic one.

9.6V is nowhere near enough for a 78L09, you'd have to feed it with almost 11V. Guessing EHX power supplies at the time were 12V.

j_flanders · Post by **j_flanders** » 21 Sep 2020, 15:47

Excellent question.
The Deluxe Memory Man says 24V on the enclosure but the power supply that comes with it delivers around 35V (unregulated/unloaded) and gets regulated down to 15V. (LM7915)
The Holy Grail says 9V on the enclosure but internally it is regulated down to 5V (78M05). I never checked the output from its power supply.
The Pulsar says 9V on the enclosure but it seems likely, because of that 78L09, that an unregulated 9V (delivering around 15V unloaded?) power supply should be used.

EDIT:
I just measured the output of my EHX Holy Grail 9V/500mA adapter: 14,95V
Here's a picture of the adapter:

I bought it at Banzai Music, the only place in Europe I could find that still sells these specific adapters.
My Big Box HG which I bought used, did not come with its original power supply.
15V regulated down to 5V might explain why the regulator chip gets so hot (+100° C). Might also explain the hiss?

I also measured an older (3.5mm plug) EHX 9V/100mA power supply : 11,95V
Too bad I can't remember which pedal it came with. My guess is a big box Big Muff or Double Muff.
Here's a picture of the adapter:

I'm surprised how much better my big box Pulsar sounds with it!
My perception(?) is: clearer, more defined, less loud, less distorted, more highs, less lows.
At the same settings the rate is definitely faster.
I always preferred my XO version, but now I'll have to compare them again.

All in all, this could explain the old EHX statement that said to only use the power supply that came with the pedal.
I simply always used 3.5mm adapter plugs and daisy chained all my big boxes from one single regular 9.6V adapter.

lolbou · Post by **lolbou** » 21 Sep 2020, 16:44

I've just checked the EHX power supply that i got when i bought my Pulsar (second hand). It's delivering 15.5VDC on its output, although it's being sold as 9VDC.

Hence the 9V regulation then.

: EHX 9V PSU.jpg (36.15 KiB) Viewed 2238 times

ps: it's the old "mono jack" plug type PSU...

j_flanders · Post by **j_flanders** » 21 Sep 2020, 17:11

That's very close to the 14.95V I'm measuring for my 9V/500mA Holy Grail PSU.
(I was updating my post above while you replied.)

lolbou · Post by **lolbou** » 21 Sep 2020, 18:12

I guess measuring the output voltages of any EHX PSU would prove useful then, and having these measurements clearly marked as well.

Maybe the Pulsar's inner regulator help smoothing any ticking power spike?

mozz · Post by **mozz** » 21 Sep 2020, 19:32

Most all cheap power sure put out a lot more with no load attached.

bumblebee · Post by **bumblebee** » 24 Sep 2020, 20:11

j_flanders wrote: ↑21 Sep 2020, 17:11 That's very close to the 14.95V I'm measuring for my 9V/500mA Holy Grail PSU.
(I was updating my post above while you replied.)

But that’s without a load, yeah? What does it draw with a load?....it will be less.

(BTW, on EHX, I’m Ned, we talked the other day in a thread

)

I have the stereo pulsar, xo size, and while I have no power supply for it it does run well on a 9v 1.600mA daisy. I usually just use batteries for low current draw pedals anyways. 17mA isn’t exactly low but for how much it’s used a battery last a long time.

I’m in AUS and unless I buy a pedal here, which is rare, I usually end up using the UK power supplies with a pin adapter as we run similar power 220/240v @ 50hertz

j_flanders · Post by **j_flanders** » 24 Sep 2020, 22:09

lolbou wrote: ↑21 Sep 2020, 18:12 I guess measuring the output voltages of any EHX PSU would prove useful then, and having these measurements clearly marked as well.

Maybe it's more useful to find out which pedals use that 7809 chip.
The pedals using the 7805 will work with any psu (9V, 12V, 24V, regulated or unregulated, all plenty above 5V)
The pedals using the 7815 or 7915 always come with their dedicated 24V psu and even if they didn't, then both regulated and unregulated 24V psu will work, as they're plenty above 15V.

It's just the ones using the 7809 chip because those might not work as intended with a regulated 9V psu.

lolbou wrote: ↑21 Sep 2020, 18:12 Maybe the Pulsar's inner regulator help smoothing any ticking power spike?

I solved that issue after reading a suggestion on the EHX forum. Here's my thread on that subject:
https://www.ehx.com/forums/viewthread/9710/

mozz wrote: ↑21 Sep 2020, 19:32 Most all cheap power sure put out a lot more with no load attached.

That's correct but it's not really the problem at hand.
This is:
Pedal says: 9VDC

But it does not work properly with this 9VDC psu (because it's regulated, supplying 9V, with or without load, too low for the 7809 chip)

It does hower work as intented with this 9VDC psu (because it's unregulated, supplying 12V, without load, high enough for the 7809 chip)

bumblebee wrote: ↑24 Sep 2020, 20:11 But that’s without a load, yeah? What does it draw with a load?....it will be less.

(BTW, on EHX, I’m Ned, we talked the other day in a thread )

I have the stereo pulsar, xo size, and while I have no power supply for it it does run well on a 9v 1.600mA daisy.

I also have the stereo pulsar and it works fine with a regulated 9V or 9.6 psu. At first sight I don't see a voltage regulator in the XO though, which might explain why.

I do remember the thread on ehx.com.

(Flanders is not my name by the way, it's where I live. My name is John.)

lolbou · Post by **lolbou** » 25 Sep 2020, 20:06

j_flanders wrote: ↑24 Sep 2020, 22:09 I solved that issue after reading a suggestion on the EHX forum. Here's my thread on that subject:
https://www.ehx.com/forums/viewthread/9710/

Did the same foil trick in a Tonepad CE-2 back in 2007 (search for LoL in the build reports http://www.tonepad.com/project.asp?id=53 )... I was more speaking about the ticks that can appear when the power is heavily loaded by the oscillator spikes though, but maybe it doesn't apply to the Pulsar. Mine doesn't tick AKAIK.

j_flanders wrote: ↑24 Sep 2020, 22:09 That's correct but it's not really the problem at hand.

It is somehow. The old Boss PSUs were unregulated and the current draw was dropping the voltage down. If you look at the EHX label, it clearly states 9VDC @500mA, but delivers 15V unloaded. The regulation is just inside the unit, not in the PSU... That answers the OP.