??Do YOU Own A Rectifier Amp That POPS??

[Storm]

Take detailed, high res shots of your circuit boards and i'll figure it out. I seriously think my mods could work. We can experiment with the value of that cap.

I would do this but my camera is unable to take good closeup high res shots. Look how the internals of the G-Major I took for another thread turned out - blurry at best

Ciao ...

 

[barneyc4]

Storm, are all your channels popping? Do you tolerate it on stage?

Or just channel 3 vintage like mine?

 

[Storm]

Storm, are all your channels popping? Do you tolerate it on stage?

Or just channel 3 vintage like mine?

All my channels pop but channels 3 and 4 are the worst. I haven't taken this amp on stage yet but the next gig is in July and I'm dreading a channel change with the amp miced up to the PA. People will hit the deck thinking it's a madman with a gun! I could take it back to the shop under warranty but then I'd be without an amp for a month or two which would be a real pain in the ***.

Ciao ...

 

[barneyc4]

Interesting....
Will it start popping when you change channels as soon as you switch the amp from standy to on or does it take a while?

 

[Storm]

Interesting....
Will it start popping when you change channels as soon as you switch the amp from standy to on or does it take a while?

It starts popping straight away but fades away slightly after a few changes. After a while of not performing a channel change, the popping comes back to full annoying level if a change is made.

Ciao ...

 

[Storm]

Does anyone else know what capacitors are needed to be changed to get rid of the pop?

Ciao ...

 

[mutha]

:arrow: jvk & boogiebabies
The most important reason of popping in RK and Roadster is switching elements being on high potential. It take place (for example) especially at first gain stage where anode resistors (220k & 100k with adequate capacitors 22nF & 47nF) are subsequently switched to anode of this stage (mention switching between II and III channel!). Huge pulses are so strong and they are feed to other stages, so muting/clamping circuit cannot stop them. BTW muting circuit is malfunctioning "at enter" because of its reverb part (mention 2-3 sec. for reverb on)!!!
J175 and relay's coils have nothing(!) to do with this problem. Another funny thing is power tubes switching.....

 

[Storm]

:? Urrggh! So what's the problem if it's not capacitors then? It's a **** joke they cost this much and Mesa release them with a problem so obvious. It really craps me off to be honest :evil:

Ciao ...

 

[barneyc4]

Storm...

The pop will live in our amps forever.


Once it pops, it can' stop.

 

[domct203]

Yea I was kinda burnt up over the pop too at first but I have yet to hear it over the stage noise, and two gigs with her and nobody else seemed to notice it either, even thru the PA. I just make sure I keep cycling thru all the channels before we start our set and so far so good.

Dom

 

[barneyc4]

Yea I was kinda burnt up over the pop too at first but I have yet to hear it over the stage noise, and two gigs with her and nobody else seemed to notice it either, even thru the PA. I just make sure I keep cycling thru all the channels before we start our set and so far so good.

Dom

So does your Roadster pop when switching channels in bedroom volume level?

 

[Storm]

According to the knowledgeable folk at 'Pro Audio' in Australia the problem seems to be;

The majority of the time (99%) the popping problem is because the muting FET (j175) is leaky. There are several of these FET's in the amp. The Mesa amps aren't very user friendly to service and can quite easily be damaged. The PCB's are multi layered and a full removal of the main PCB is an hours work to someone who is very familiar with them, to remove the components from the top can lead to inducing other faults.

Looks like I have to find my receipt and get it repaired under warranty thus miss having my amp for a while which is going to really crap me off no end considering our band is gigging really soon :evil:
Such is life, they say :roll:

Ciao ...

 

[jvk]

Hmm interesting. I've heard that only some J175s are supposed to be noisy. I guess with a scope you can test them all out and look out for any that cause a messy spike.

The board doesn't have to be removed to swap out the parts as it's alot of hassle to desolder all of the wires. You can desolder parts from the top by being very careful and patient to make sure that all of the solder's mopped up. It helps to heat up the joint once more just before removal so that any remaining solder is liquified and and the copper traces aren't peeled off when pulling out the part.

 

[Grendeltone]

The reason they give to some people for the popping in their 3ch Recto / RK / Roadster is ridiculous... static build-up?? They're full of crap... here's why...

When the amp's channel select switch is on footswitch mode and the amp is powered on, notice how none of the channel LEDs on the amp/footswitch light up until one of the channels is selected. That means that none of the channel selection relays are turn on. Bearing that in mind, the muting circuit only comes into action when the relays are turning off. So the first time you turn the amp on none of the channels are selected so the relays associated with them aren't on to begin with, and so switching to another channel doesn't turn any relays off and so doesn't trigger the muting circuit. Simply put, one of the channels needs to be selected first before the relay muting kicks in. It's got NOTHING to do with static buildup. They could've easily rectified this by adding a circuit that selects one of the channels when you first power it up.

Consistent popping whilst switching is something else. There are lots of other amps that are packed with relays; Peavey have been stuffing their amps with relays for years, the 5150 is dead quiet. Diezels, Marshalls, Bogner and VHTs all use relays, yet no pops.

Here's how the switching sequence works: when the channel selection is made, some relays are turned off and others on. The relays turning on remakes the circuit continuity almost instantaneously and generates a sudden increase in the signal level, which when amplified is heard as a pop. In the relays which turn off, the collapsing voltage across the coil generates a voltage spike, which triggers an RC timing circuit. The RC circuit turns on muting transistors which drive the signal to ground with J175 FETs, and so suppressing the sudden spike in the audio signal.

Ideally going 'switch+pop+mute' to 'unmute' is supposed to take 10-30ms, depending on the switching speed of the relays, with 30ms being the norm with most manufacturers. It could be that this time period has been set too short. Or like Boogiebabiez said, the FETs are misbehaving. I think it's most likely the former.

Solutions
Increase the RC time constant. The RK/Roadster and Recto have R=100k and C=.1u, giving a mute of 10ms. Increasing this to ~20ms more might work, with setting C=.22u. Downside is that the muted gap in the signal will become more obvious.

Replace FETs with better quality ones. There's at least a dozen of them in the RK.

Or live with it?

Even though I am not suffering from pop.. thank you for your informative contribution..

 

[jvk]

8)

 

[DS-1]

Mine (a '05 Triple Rectifier) doesn't pop, but has a little mute between the switching (it's difficult to ear it live, but if you record your amp while you switch channels, you can ear the short "silence" in the changing). BUT I have to say that it popped in the first months of use, maybe because I turned on the amp, leaved the stand-by and then started to change channels. Instead now I turn on the amp, then I change 2-3 times channels and then leave the stand-by.

 

[Dale B.]

Yes, I've owned several that did it. After balancing out my channel volumes, I hardly noticed it or it completely went away. That may or may not work, but it always has for me.

*SHRUGS*

Dale