Quote from: Tassieviking on February 25, 2022, 04:48:13 AM
I wonder if most upcoming groups in the future will use mainly SS amps like these ?
Why would a young person spend 10x that amount for a tube amp, I think the music scene will change very soon.
If a young band builds up their style and sound with SS amps why would they ever to to tubes ? It would not sound right to them.

Yeah have fun trying to source the fancy chips when they stuff up.
Keep in mind these fancy digi tricks are run by chips which may well be obsolete in a few years so sourcing parts when they fail  might render a lot of this stuff land fill with in a decade or so.
Mean time all the older analog stuff (SS or Valve) which are mostly simple designs will still be repairable.
There has already been quite a few failures of these hi tecky digi does it all rigs.

@ Joecool well honestly I watched the vid on the link and I did not here anything that would make me want one.

Then when it mentioned the App crap to access all the other stuff I lost interest even more so.
Have fun trying to use that live. :lmao:

But yep the younger gens will love the novelty aspect of it till it wears off. Or they actually get to play an old school big Amp that is well designed then they will realise there is no substitute for the real thing.
If you need FX,,, they are called pedals.
The problem with the ALL in ONe concept is you are stuck with it. 8|
Whereas spending your money on a simple quality Amp you then have the option to add whatever pedals/Fx you want.
If not happy you only have to purchase another pedal which is far cheaper than the purchase of another Amplifier 8|

Call me an old fart but I've been in this game for a very long time and you get to know what works and what is just fad phase.
Rant over,, Phil.

For clues on the subject Google "Reamp box".
There are a few DIY circuits around if you search,, I have no idea how well they work.
Just download a few guitar tracks and play back through a reamp unit into Pedals/Amps.

I found this with a search and likely many more exist.
https://www.youtube.com/watch?v=b1O_5gaX4-s
Phil.

As I'm not sure exactly what you meant 
So does the Bad Rev Tank work when run by the good PCB?
Is that what you mean?
Phil.

If the reverb is weak then I doubt the reverb tank is at fault. The way the reverb Driver is setup it would be a very weak signal that drives the reverb tank.
As with a lot of reverb circuits (even some used now) the Drive is Critical to performance.
the schematic shows the reverb Drive is taken straight from the passive input, only relying on 2 transistors,
So it will be weak.
Adding even more problems is the return is also passive.

If it was me I'd rebuild the reverb section or just use a pedal
Phil.

Scroll back to post 19 :tu:
Phil.

Great to hear you have resolved the issue, I know how hard it is to understand the intricacies of these things when you are new to it all. :dbtu: :dbtu:
And YES leave the Mains Earth wire connected to the Chassis, It's always the first thing I check when working on gear.
Keep at it, the next time you have a bad hum you will know what to look for :tu:
Phil.

If the amp makes exceptable sound and all the controls work as one would expect then it's highly unlikely there are other faults. 8|

The fact you isolated the input and found it reduced the hum tells you the issue is most likely a ground path problem.
And after studying the pcb pictures it's a poor layout and I'm not surprised it has a hum.
As far as mods go without another Amp or schematic of same you have no way to know what was stock.

If your intention is to sell it then just fix the hum and don't waste your time.

If you keep it and use it as a learning tool it will help you down the track.

Long before I fully understood Amplifiers
I once had a little 10 watt amp and tried to modify it. By luck more than brains I fluked it into a great little sounding amp. For the first time I actually sounded like Clapton with my strat.

Silly me sold it for another rig that had reverb but I never drew up the schematic. I still regret not keeping it and drawing up the circuit before I sold it. That was 40 years ago and I still regret it now.
Phil.

Oh adding this to show the idea of ground paths in amplifiers.
Note, How Com 1 is the Central Com point for the whole Amp, High current paths come first (The Lm1875)
THEN the low current paths from the sensitive inputs come last and preferably on separate tracks.

Makes  me smile Enzo, Yep my bin is the perfect size for a 12" speaker. :cheesy:
If I want to get an idea of how big to make a box I shove pillow in the bin which of course alters the volume.
Oh I do empty the bin first :lmao:
Phil.

Before we go rewiring the whole ground path, just start with one mod at a time, that way you can assess progress.
Ok isolating the input socket has helped so leave it isolated and Re route that Yellow Com wire
to the Common/Ground junction of the 2 main filter caps on the PCB. (see pic)
You will need to drill a hole for that wire and scrape off the lacquer to solder it.
(while you are there drill 3 holes as you may need it for other mods).

Note the common junction of the main filter caps becomes Com 1, ideally every other com point
should go back to Com1 on a separate path and then Com1 junction is wired back to the chassis
case. (where the yellow wire was) Don't worry about inserting a chassis wire right now as the PCB
is already grounded via the mounting posts and could lead to more problems.
I'm just saying this to show you how it should be done.
Google star grounding for clues.

Rewiring the yellow will alter the Current path and might be enough, if not then you may have to alter the path for com 2. (blue wire on picture) At the moment it seems to run all the way around the out side of the PCB then back to Com1,, which is not a good design. xP
To do the Com2 rewire you will need to cut a pcb track so meantime, Can you tell me if the ground trace runs all the way along the front edge of the PCB and back around to the main filter caps?
I can't clearly see the front edge with all the pots . It looks like it does but i need to be sure.

So Yellow wire mod first and see if it improves,, then move on from there. :tu:

You seem keen to learn so maybe sit down and draw out the whole schematic,, ,yeah it will be slow but you will learn a lot.
BTW, be aware electronics can be very addictive. :duh
Phil.

Great work you are doing well. :tu:

Ok isolating the in socket reduced the hum so you know ground path is an issue.
I did look at the first PCB pics again last night and Yes there are many ground paths. ouch!
It's likely that this being a budget model there was no R&D done so the issue may well be a factory fluff up,,, I've seen that a few times even in higher end products.

I've got things to do today but later tonight I'll edit some of your pics with possible re routing of the ground paths.
thanks for the new pics it will help us understand just where all the ground paths run.

the issue of ground loop hum is not the voltage diff but more about *high Current and low Current* mixing in the wrong place. Input ground path is very sensitive and can be easy pick up the hum if the ground paths mix.
something like that,,better minds will explain it better. lol.
More tonight, Phil.

Good, then reverb is not the source of hum. :tu:

Ok I've looked at the pics all over again,,,
Now one possible Ground loop I can make out is in a second ground right at the input socket.

It looks like the 2 Red ac wires coming from Power Tx go to the PCB BUT!!! the Common seems to be the Yellow wire which goes to the chassis I assume??. (remember I'm only going on what I have in front of me)

Normally the yellow wire would go Direct to the PCB.
This means the PCB has to be mounted for the amp to work.
Ok so far it's valid. BUT you then have the input socket grounded to chassis as well.
It is possible that may cause a hum loop.
I'd try mounting it all back except for the input socket which I'd leave floating, then see if the hum stops.

If so you will need to change the socket to an Isolated unit.
The original socket may have been a failing isolated one (Plastic) and replaced with a metal one.
It's all just a hunch but simple to test.

If it was mine i would rewire that (I assume) Common yellow on the PCB right between the Main Electro Caps.
Phil.

Quote from: cin on January 15, 2022, 07:16:50 PM
The IN is clean, the OUT is dirty.

Just to check we are on the same page 

The INPUT RCA on the Tank is the DRIVER end (the signal thsat excites the springs)
The OUTPUT RCA  on Tank is the Pickup end (this picks up the reverberation of the springs and sent back to be mixed with the dry signal)

So Rev drive OUTPUT on Amplifier circuit goes to the Tank Input/ Drive.
And Rev return /Pickup circuit on amplifier goes to Tank Output/ Pickup.

The idea here is to divide and conquer,, you remove as much of the aux circuits as you can to narrow down the problem.
If you remove the Rev chip and the circuit still hums then you know to look elsewhere.
Keep at it you will get there.   
 

Yes,
Just like an unplugged guitar cord,, they hum a bit and when you short the tip to the sleeve the hum stops.
If there is a dodgy ground connection in the tank then this removes the tank from the circuit.
So pull the RCA plug on the *PICKUP end of Tank (output of tank)* and ground the tip to the chassis on amp, or short tip to outer ring with a screwdriver or something metal.

There is a Drive end and a Pickup End on these tanks and can be confusing.  :loco
So Drive is the input on the tank,, and PU is the Output from tank.
If you touch the drive tip on rca you wont hear anything.
The PU end is an aux input back to Amplifier so you can hear the reverb.
Phil.

Quote from: cin on January 15, 2022, 07:16:50 PM
The IN is clean, the OUT is dirty.

So I pulled out the tank and took some measurements inside, the signal wires going into the IN coil is clean, the signal wire coming out of the OUT coil is dirty. The OUT coil does look like it may have overheated, the tape is discoloured in one spot. Is that a thing? Can a small coil overheat if it's overstimulated? Would that indicate the amp was shaken vigorously while On?

So I'm guessing I'm stuck replacing the whole tank, it's all pretty much riveted together...

THANKS GANG!

You said the tank was wired in reverse,,,,,,,,,Well that may well have overheated the coil. 8|

If you suspect the tank is the issue then disconnect the pickup cable and short the pickup end.
Now test the amp to hear if the hum/buzz is still present.
If it greatly reduced the hum then you just found the problem.

If no luck then I would just remove the reverb chip as it could be failing from driving the wrong load.
Phil.