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Messages - joecool85

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Amplifier Discussion / Re: Roland Jazz Chorus 50 troubleshooting
« on: September 17, 2021, 09:00:25 PM »
Hi, guys.

It's been a few years since my last visit, and I'm happy to see the forum thriving.

A few weeks ago I was lucky enough to catch a guy in the act of throwing a pristine looking 1981 Roland Jazz Chorus 50 in the dumpster. I managed to stop him, and brought the amp home with me. However, not all is well inside this thing. The JC-series is known for their clean sound. This one will break into some nasty sounding distortion, even when playing soft with weak single coils. If I turn the guitar volume down to almost zero it does not distort, so it does react to dynamics. Also, the chorus effect and the reverb is not working. The Vibrato works as it should. Plucking the springs in the reverb pan comes thru loud and clear. All other controls seem to do what they are supposed to to.

The amp uses the same circuit as described in the second half of the service manual found here :

Here is a little video of the amp, showing the distorted sound.

There is no sign of bad solder joints, burnt components or bulging caps. I will recap this thing, but I want it up and running first. I don't think the problems are caused by gone electrolytic caps.
As far as I can see from the schematic, there is no logic in that both the reverb and chorus not working. Can anybody take a look at the schematic and help me with where I should start troubleshooting?

Any update on this amp?  Curious if you got it sorted.

Also, welcome back!

The Newcomer's Forum / Re: Hello
« on: September 17, 2021, 08:58:03 PM »
Welcome aboard!  I'd love to see pictures or video of some of your past projects!

The Newcomer's Forum / Re: Which replacement power cord?
« on: August 17, 2021, 07:12:17 PM »
That'll work well. Actually, any IEC power cables would work equally well for home and information products. Always use cords with a wire gauge of 0.75mm2 or greater(I dunno how much AWGs it equals to ... In my country, we use squared millimeters instead of AWGs to measure wire gauge ) to ensure an abundant supply of current and to eliminate risks of fire.

0.75mm2 is 18 gauge.  I wouldn't use anything smaller than this either.  At the length most power cables are (3-6' or 1-2M), they can push 15 amps very safely which gives 1,800w at 120v - way more than most of us would ever need!

Honey Amp / Re: Thoughts on my new Honey Amp
« on: August 05, 2021, 03:48:15 PM »
Hi there, I am interested in the Honey Amp kit. Where can I purchase please?

PM Sent.

Honey Amp / Re: Thoughts on my new Honey Amp
« on: August 02, 2021, 11:41:07 AM »
Hi there, I am interested in the Honey Amp kit. Where can I purchase please?


I'll be adding a web store soon to the site so you can purchase there.  If you'd like one sooner than that, please PM me and we can do a direct sale.

Honey Amp / Re: Power supply suggestions
« on: July 31, 2021, 09:14:30 PM »
Worrrd, I think I figured it out.

Much Appreciations!

Glad to hear it!

Honey Amp / Re: Thoughts on my new Honey Amp
« on: July 31, 2021, 09:13:33 PM »
" No power switch, but I can understand the omission, since this is supposed to be highly customizable. I have to pop the battery connectors to power down, but my enclosure choice makes that easy enough"

You could try a 3 prong switching jack that disconnects the battery ground when no cord is inserted.

Like pedals use.

Or just wire a switch inline with the battery - that's what I do.  I'm not a fan of onboard power switching, even when it is for a battery amp.

Regarding power output, it is an LM386 so it's about as loud as I could get it.  If you need more headphone volume, try using a lower resistance value for R10.  If you use 10 ohm it should just about blow your ear drums with any normal headphones - mine certainly did!

I'm planning another battery based kit, probably power amp only.  This one would be based on the PAM8302 which gives 2.5w and runs on a really low voltage of 5v nominal.  I've been playing with the board from Adafruit and it's significantly louder than any LM386 circuit I've used.

Amplifier Discussion / Re: My K-20X
« on: July 21, 2021, 03:13:16 PM »
That solid state amp does not require a load, you can simply turn off the speaker with a switch.

What I would do is connect the line out 10k resistor to the phones jack tip connection instead of the speaker.  Now the line out works when you are on speaker or when on phones.  Now the phones still work, but you can use the phones jack to kill the speaker.   Just plug an unwired plug into the phones jack, and that opens the speaker connection.But a switch works fine too.

Enzo, that's a pretty slick idea! I'm not going to re-wire mine since I rarely use the line out now anyway, but if I ever did another I would probably do it this way.

Honey Amp / Re: Power supply suggestions
« on: July 20, 2021, 10:26:25 AM »
Right on.

It's these details in certain facets of life, that somehow tend to escape me....

I just wasn't sure if there may have been something pre-designated on the board, for executing such a mod/addition.

Thank you!

Nothing on-board for this, just ground and positive input voltage.  Like Phil said, you would need to do this offboard like most pedals.

The Suhr Discovery Analog Delay has been released.  It looks to be an absolute beast of an analog device: built with old-school bucket-brigade IC tech, can store up to 127 presets, 17-2000ms delay range with digital readout, tap tempo input, multiple division modes (1/3, 1/4, 1/8, 1/16), and an array of controls.  Plus it is built here in the USA and looks to be made of sheet steel stamped into an approximation of a 1/32 scale Sherman tank.

This looks to be a very professional piece of kit, and comes with an appropriate price tag coming in with an MSRP of $549 USD.

The Newcomer's Forum / Re: Just joined...
« on: July 07, 2021, 11:00:56 AM »
Hello to everybody..Just joined the forum...I see some members are also members of another forum...anyway, will read some of the posts and eventually will get my feet wet.....and have fun....

Welcome aboard!  Feel free to share what gear you have and what type of electronics/amps/guitars etc you are into, we love to hear it!

Amplifier Discussion / Re: DIY solid state amp kits?
« on: July 06, 2021, 03:20:02 PM »
Wish I could post pictures. It would so help answer your questions. I have the original circuit diagram. I can't tell what the wattage is. I would hazard that the voltage rail is 12-15V.

You can post pictures :-)

Please measure the voltage with a DMM and let us know the result.

Amplifier Discussion / Re: DIY solid state amp kits?
« on: July 04, 2021, 09:01:43 PM »
I plan to keep the transformer from power supply,and the reverb. Everything else to be rebuilt.

To help with this, we will need to know the voltage on the transformer's output as well as roughly how many watts the original amp was suppose to be.

Honey Amp / Re: Power supply suggestions
« on: June 30, 2021, 10:03:27 AM »
....and, on that note.

Here is another Matt, with the exact opposite experience. Hahaha!

I couldn't find a decent enclosure, so I happened to find this Kleenex Box randomly, so.... Yep. I stuck it in a Kleenex Box.

For now, at least.

That is fantastic!  Does it sound okay in that box?

Amplifier Discussion / Re: Pedal Hiss?
« on: June 28, 2021, 10:44:26 AM »
If the Hiss is only present when using the converter then logic tells you there is a very good chance it IS the converter.

Be aware, If it's a Switchmode type DC/DC converter then it's a fair bet that is the source of the noise. In which case it's highly likely the converter is introducing hash as Smode setups are notorious for bleeding HiFeq crap into Audio gear.

If so you may be better off building a simple Analog regulator, i.e. using an LM7809 reg chip.

Also please consider that the explanations you give make sense to you because it's in front of you,,, we are not there so it's often hard to make out what exactly you mean.


I agree it is most likely the SMPS (switch mode power supply).  Sometimes you can add some filter caps to remove this noise - it depends how bad it is.  Worst case you can always go with an analog regulator like Phil mentioned - I just hate how inefficient they are.

Here are some good ideas for how to set up your filtering:

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