Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.

Messages - Rockhorst

Pages: [1] 2 3 ... 35
General Questions / Re: Sparkle drive/green Rhino...
« on: March 03, 2019, 10:43:21 AM »
The Sparkle Drive is a screamer, the Green Rhino is a

Breadboarding won't hurt your wallet or anything else, so go for it.

The 4558 was looking good on the DMM but with no sound coming through I thought that maybe something else shorted out as that cap was losing its mind. So I decided to replace it once more with a socket (should've done that in the first place). That way, future repairs on the IC won't damage the board.

It's 1:00 AM right now. I'll continue tomorrow (vacation time, so let's hope I fix it this week).

One step forward, one step back...I should've paid better attention, but when replacing the power filtering electrolytic cap I installed it with reversed polarity. On the original cap, the plus-side was marked instead of the standard minus side these days. Could've spotted that, but I blew the cap. Replaced it and the wire from the board to the switch had become detached. Fixed that. Desoldered the transformer, replaced the 4558 with a socket and installed a fresh chip.

Good news: power is now at 28V from the EHX supply to the board, 1st opamp sits at 6.7V bias, 14.6V input. So that seems fine. The clean signal is now very very faint however and most likely only induced in the wires, not really going through the switch. Probably another silly mistake somewhere.

Well if it's broken... cut the wires and test your theory ;)
Yeah it was just dawning on me while I was typing the post. Will test this soon, it makes sense.

I'd like to keep the original regulator setup. I measure the voltage at the point where I clip it to the board. The old transformer is still attached. I was thinking that maybe, if the primary is broken but the secondary is still ok, that could be pulling down the supply because there's a lot of current flowing through the coil? I haven't noticed it heating up though.

I can connect it to a Strymon Ojai or PP2+ for 18V. Just to be double safe: I can use a 'regular' 18V supply, ground to ground and +18V to the power input?

I attached the wire from the boost switch to the board, replaced the top 4558 IC and the larger electrolytics. Sure did something. I can now blend between input signal and 'whine' signal and the boost also works. Here are some fresh measurements:

Voltage at board input: 11.6 V (as before), but supply voltages on the ICs have come down to about 9.5V.

4558 closest to the jacks
Pin 1: 4.9 V
Pin 2: 4.1 V
Pin 3: 4.1 V
Pin 4: 0V

Pin 5: 4.3 V
Pin 6: 4.4 V
Pin 7: 4.4 V
Pin 8: 9.7 V (no longer equal to supply?)

4558 middle of the board
Pin 1: 3.5 V
Pin 2: 3.5 V
Pin 3: 3.5 V
Pin 4: 0V

Pin 5: 2.4 V
Pin 6: 2.4 V
Pin 7: 5.5 V
Pin 8: 9.8 V

Thanks for all the help so far and apologies for taking so long to get back. I really only have a few minutes a day for this kind of thing at the moment...sigh.

Anyway, rechecked: I made a counting mistake. Pin 10 and pin 11 both at half supply after all!

Next baby step?

pin 10 is at half supply (5.8V), pin 11 is at full supply (11.6V)

So without a load the EHX wall wart sits at 34V. Connecting it to the MM it drops to about 14V. The input of the regulator is at 12.6V, middle pin is 12V and the output is 11.5V. I'm guessing those numbers are off ;)

Whine changes with delay pot, goes supersonic when turning delay time down.

4558 closest to the jacks
Pin 1: 5.5 V
Pin 2: 5.5 V
Pin 3: 5.5 V
Pin 4: 0V

Pin 5: 0 V
Pin 6: 10.6 V
Pin 7: 11 V
Pin 8: 11.6 V

4558 middle of the board
Pin 1: 4.2 V
Pin 2: 4.2 V
Pin 3: 4.2 V
Pin 4: 0V

Pin 5: 5.8 V
Pin 6: 4.8 V
Pin 7: 11 V
Pin 8: 11.6 V

So that looks like both the b-sides of the chips are not doing what they should be doing.

Only had time for a quick power test. When powering the effect you clearly hear a high pitched whine that starts up almost immediately and persists. This is usually followed a few seconds later with static noise (from a delay line?). No audio probing yet, that's going to be the weekend.

[one thing I noticed is that approaching the -24V probe to the center tap produces a little spark between circuit board and probe. The outer tap does not]

Open Discussion / Re: Going for broke (healthy eating thread)
« on: February 11, 2019, 05:19:13 PM »
A steady weight loss of no more than 1 kg a week is 'healthy'. I can't diet for shit. I need to do sports with it, but I find less and less time (and motivation) to get into it. I have a racing bike and I should start somewhere this month for cycling to work in the spring (30 km one way). Hoping to drop 10 kg again this summer.

Anyway, that plateau is nothing to worry about. You went down fast, maybe too fast, initially. Your changing your lifestyle, takes time. Think about how it makes you feel better, that's the important part for now.

Thanks for chiming in Scruffie :)
The reason I mentioned mods is that I saw some components that aren't on the circuit board but rather fly over it. I just assumed they where added later.

Which terminals should I attach the 24V supply to? Referring to picture 03 in my original post, I would say that the top wire is for the ground terminal (outer sleeve of adapter)? Center tap is for the LED, so -24V on the bottom connection in the picture? Power is then very crudely rectified by those 2 diodes, right?

Open Discussion / Looking for help with an actual vintage EHX Memory Man
« on: February 10, 2019, 05:52:11 PM »
note: pictures of the unit attached.

Someone sent me an early EHX Memory Man hoping I can repair it. I'm a bit apprehensive to start working on it, so I hope someone with experience with these units can help me out a bit. It looks like there have been some modifications over the years, the transformer is dead and there's a loose wire coming from the boost switch. No clue if the delay chips are still good. Still looking for a verified schematic for this particular unit.

On the EHX forum I found that a replacement transformer for the DMM is the F-115X which Mouser carries. I'm going to compare some specs, but I expect it will work with the MM as well. I have a EHX 24V center positive wall wart, was wondering if I can use this to test the unit before buying the transformer.

Any other suggestions for testing the unit are very welcome.

Open Discussion / Re: Ibanez Super Metal SM-9
« on: January 28, 2019, 03:53:09 PM »
Tiny update: I've bought a second hand Maxon 4-knobber for some real life testing. Will keep you posted :)

Pages: [1] 2 3 ... 35