Colorsound Power Boost 18v... Annoying ticking noise.

[Electric Warrior]

The original unit probably used low gain transistors, [...]

Why would you assume that? When they used transistors assigned to a gain bucket, it usually was C.

[amz-fx]

Why would you assume that? When they used transistors assigned to a gain bucket, it usually was C.

Not assuming; I saw it mentioned in a massively long thread on another forum that I scanned before posting. It may well be wrong, and I saw different transistor numbers noted on different schematics. One poster claimed the schematics were wrong but I did not go through the whole thread to see if the corrected version was posted. 

For the OP, it would be easy to just clip another 220pF in parallel with the first one to see if that has any impact.

Best regards, Jack

[bettsaj]

I would try that.... But my board is dead now, at least for the time being.

I'm building another board, and as stated previously i'm only going to populate the pre amp section. I'll then run a test to see if it motor boats. If it does, i can conduct trials on just that partially built section of the circuit.

Stu Castledine has amazingly emailed me back and told me that "it is a proven design, so it should be possible to make it work with the standard parts values" he also said "I've never had this problem and I've "thrown together" well over a hundred Power Boosts"

With that being the case, and using the exact same component values as him, this should work no problem..... Unless a component is faulty, or the board has been etched incorrectly.

I have tried all manner of values on the input etc and nothing has worked.The only thing I haven't been able to do is connect it to an Oscilloscope, which if this third build doesn't work is my next port of call. I will try increasing the 220pf cap value to 440pf, although I don't think that is the issue.

When you look at other schematics on the web, you'll notice there's hardly any for the power boost, they're nearly all for the Over driver which is a totally different beast all together. That does have different component values, and may well have a different cap value across the base and collector of Q2 (although in the schematics I've got it has the same 220pf as the power boost). Other forums I have read have been giving confusing information around the power boost and the over driver as they are similar... But very different.... I've been very wary about what i've read as a lot of the time they've been discussing the power boost but been quoting specs for the overdriver.

I've had an unhealthy obsession with the power boost for ages now, and have researched sh*t loads about the pedal...... There must be a fundamental similarity between my 2 pedals that don't work...... the only similarities are the transistors and the electrolytics.

When I build my third board I'll be using transistors from a different source. The last lot were from EBay, and although i'm sure I haven't been ripped off, my suspicion has been piqued.

As someone said on the E14 forum:

To quote Sherlock, "Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth." that must be where we're at right now

I tend to agree.

You can check that forum thread here.... I've had tech heads from all over that forum helping me with this, which I've been feeding back here.

https://www.element14.com/community/thread/60782/l/colorsound-power-boost-noise-issue

[bettsaj]

Why would you assume that? When they used transistors assigned to a gain bucket, it usually was C.

Not assuming; I saw it mentioned in a massively long thread on another forum that I scanned before posting.

Best regards, Jack

If it's the thread I read a while back, one of the guys on that thread was saying Electric Warriors schematics are wrong... They're not. The guy on that thread was getting quite %^&*y, but then presented an over driver schematic, which bore no similarity to a power boost schematic.

Can you post a link to the thread?

[amz-fx]

I didn't save the link but that could have been it. The links to many of the schematics there were dead so I couldn't check them out.

The 220pF may not be the issue but it is easy to try if you continue to have the problem. With high gain circuits like this one, layout and ground connections can be tricky too, as has been mentioned. You would think that the original layout would not be a problem since it is proven, as Stu said.

I'm sure you have made sure that the pots are not touching the pcb tracks but it doesn't hurt to keep an eye on that also.

Best regards, Jack

[Electric Warrior]

If it's the thread I read a while back, one of the guys on that thread was saying Electric Warriors schematics are wrong... They're not.

Must be that thread over at metropoulos amps forums. 
There's actually quite an interesting schematic out there that is unlike any pedal I've seen. It's the factory schematic for the Overdriver.  It predates the 9V version of the pedal about a year. They changed how the 10k/12k feedback resistor connects when they moved on to the 9V version, but the factory schematic shows a third way to connect it.

It mentions BC109s, but I've never seen those in the wild either. In 18V Power Boosts I've seen BC108, BC184L and BC169C. In Overdrivers (9V) BC184L, BC184C, BC169B, and lots of unmarked ones. So it was mostly unmarked gain buckets and high-ish gains.

As your voltages are in the right ballpark we've assumed that the hfes are probably in the correct range. They're still worth experimenting with, though.

When you look at other schematics on the web, you'll notice there's hardly any for the power boost, they're nearly all for the Over driver which is a totally different beast all together. That does have different component values, and may well have a different cap value across the base and collector of Q2 (although in the schematics I've got it has the same 220pf as the power boost). Other forums I have read have been giving confusing information around the power boost and the over driver as they are similar... But very different.... I've been very wary about what i've read as a lot of the time they've been discussing the power boost but been quoting specs for the overdriver.

To add to the confusion, Colorsound changed the name from Power Boost to Overdriver when they moved on to the 9V version, BUT around 1976 they put some 9V circuits into Power Boost enclosures. 

[bettsaj]

Hi Jack..... Yeah that sounds like the metropoulos forum post. The guy posted the factory schematic for the Over driver that Mr. Warrior is talking about, and proceeded to say that the Power Boost schematics drawn by Warrior were incorrect...... obviously didn't do his homework.... It's not a Power Boost schematic..

Mr. Warrior, I know about that....In the mid to late 70's the 9v power boost came out, did it sound like an over driver?? As it had less headroom due to only being 9v, i'm assuming that it went into over drive earlier on the volume pot than a Power boost

[Electric Warrior]

Yeah, of course. They used exactly the same boards as for the Overdriver.

I haven't had the chance yet to compare the different versions of the circuit in person. Not much of a difference in this clip:

https://www.youtube.com/watch?v=mnm2RgfyX5Q

I still need to score an Overdriver. As I already have a Power Boost, my motivation to build one is rather low. 

[bettsaj]

Once I get the Power Boost complete and working fine, i'm seriously thinking about installing a master volume

[amz-fx]

The 10k/12k resistors are interesting. I saw different connections for them when I was looking at schematics and wondered whether it was a tracing error or not.

regards, Jack

[bettsaj]

I believe I've solved the issue, and that the root cause was possible board/etching integrity, and also maybe iffy soldering.

I've revised the artwork for the trace, which has been posted, and re-etched a new board. I've populated just the pre-amp stage and the result was perfect.

Print this image out 100% on A4, it's better coming off a PDF but DIYStompboxes don't offer the facility to upload PDF's..... If you'd like the PDF contact me.

[bettsaj]

I still need to score an Overdriver. As I already have a Power Boost, my motivation to build one is rather low. 

If you want a board I can send you one 

[bettsaj]

I have a few updates, which is really making me think there's something untoward going on with my house.

First update is, I sent my "vintage correct" board to a guy over at the Element 14 forum, he lives in Scotland, and is an electronics engineer. He took my board connected it to an Oscilloscope and nothing was wrong. He then connected it up to an amp, and a guitar and the power boost pedal worked faultless, with no issues. The only noise he had was in his words "humming coming from the cheapo guitar". This has made me feel stupid, as there doesn't appear to be anything wrong with the pedal.

He's now going to send me some videos before he returns it to me. Once i receive them I'll share them here.

Secondly, Ian Dempsey in Australia has made a Power Boost from my PCB layout and it works faultless with no issues. The only difference is he used the photo resist method to make the board, where I use the transfer method.

Thirdly, I built another board using an upgraded artwork. The results are in the below video...... I'm now officially at a loss.

[bettsaj]

The issue is now officially solved.

The cause of the motor boating was................. SKY Q!!!

Check the video below..... It took 4+ weeks, but I got there in the end.