Quote from: Lobsterjoe on January 10, 2024, 02:47:17 PMJust got an '06 Trademark 60.  At power-on, there are continuous popping and whooshing noises.  Consistently, it goes away after about six minutes.
Power cycle and the noise returns but then lasts less than a minute; unless the amp's been powered for an hour or more-then it's fine after restart.
All other functions work and amp sound normal except for addition of noise.
If I plug guitar into the effects return, the noise stops and guitar sound is fine.
Cleaned all the jacks, visually inspected PC board, jumpered the FX loop jacks (no effect on noise).
Channels settings, boost level and reverb level don't affect the noise level, but master EQ does. The character of the noise doesn't change-just how loud it is proportionate to the EQ cut or boost.
Tech 21 was responsive to my inquiry and said they haven't seen this before. Suggested I send it in. Being in California, the round trip shipping even for chassis only will be almost as much as the bench charge. Reminder: other than switches and some caps/IC's, most of the components are SMT. Comments welcome.

Given that the noise is modified by the tone stack, that means that it is happening before this point in the circuit.  Starting there (at the tone stack), working your way backwards towards the input jack.  Something between here and there is either fried, or has a cold solder.  Odds are it is a cold solder.  Careful inspection of the potentiometers as well as any caps and ICs that are through hole components in this area (between input jack and tone stack) and I think you'll find the issue.

You can also share close up pictures of the board and we'll see if we can help.

Quote from: Maddus on January 12, 2024, 04:22:45 AMOk, thanks. Would I also hear that oscillations if they happen?
I hear some background fuzz underlying the notes.

Typically opamp oscillation is above the hearing spectrum, nothing you would be able to reproduce through a speaker or hear.

Quote from: WimWalther on November 03, 2023, 11:30:08 PMHi folks,

Is there any point in changing out the 4558s in a (first model, mid-1983) Peavey KB 300?

Is there much of anything to be gained by this? The amp works fine, though it's maybe a bit noisier than I'd wish.

Thanks!

What are you going to swap in place of the old 4558s?  TL072?  For what it's worth, those old 4558's are considered magic by many.  They aren't though, they just have an awful slew rate and are kind of noisy.  The DO happen to work well for electric guitar though.

Quote from: saturated on November 02, 2023, 07:29:17 PMall i know or think is zener diodes are kind of like backwards diodes...idk 

 

Almost.  Standard diodes only allow current in one direction, zeners can flow in both directions.  Zeners will operate similar to a standard diode in forward mode, but in reverse at breakdown voltage they allow current without letting out the magic smoke.

Quote from: WimWalther on October 28, 2023, 01:15:24 AMHowdy,

I just picked up a KB 300 for a song. The unit is really nice, but the controls are dirty and the cord jacket is cracked just outside of the Heyco grommet. ETA: Cord is fixed.. Had to cut off 1" and re-set the cord in the grommet.

So the chassis needs to come out but I'm not having much luck. I found 4 screws on top (chrome strips) and 4 more in the back that secure the chassis to the case. Also unplugged the speakers & reverb tank.

The chassis can be shifted a bit, but won't slide out the rear.. what am I missing? More screws somewhere? ETA: Got it. Was hanging up on the edge of the chassis.

Also.. this is the early version (no XLR input), built in mid-1983. It doesn't have the pair of 5W resistors on the back of the tweeter horn. Should these be added, for safety? Do you know the correct value(s)?

Thanks!

Regarding the tweeter resistor: for safety, no I do not think it is necessary.  I would need a schematic to confirm this though.  Typically those resistors help to shape what frequencies are going to the tweeter.  If you like how it sounds now, you can probably leave it as-is.

With Axe FX being around for 17 years, Fender has finally decided it's time for them to jump into the arena.  Being that Fender is a very traditional company, this isn't very surprising.  That said, this isn't just a little toe dipping into the water, this is a big SPLASH!  The Tone Master Pro is a full-on modeler featuring an 8 core processor, over 100 amps models, 60 second stereo looper, 7 inch digital display, and built in 4x4 USB audio interface.

MSRP is $1,699.99 USD.  With this price, it is definitely for the gigging musician rather than hobbyist.

Fender has also released two full response self-powered cabs that are made to pair to this.  The Tone Master FR-10 and FR-12, both with 1,000w of class D power.

https://www.gearnews.com/fender-tone-master-pro-floor-revealed-a-new-helix-killer/

Quote from: saturated on October 10, 2023, 11:49:46 PMI am really enjoying this set up

very much so

but apparently this Crate Amp was neglected and not played enough and in need of some love

because this slide switch has been cutting in and out and off and on...but getting better with some exercise

You cannot view this attachment.

It probably needs to be cleaned.  Personally I'm not a fan of slide switches at all, mostly for this reason.

Quote from: FleshOnGear on September 23, 2023, 05:47:05 PMThe are some big positives for this amp. The cabinet is sturdy. Even stock the clipping circuit is sufficiently tube-like in tone. And, these are relatively cheap on the used market. Just a few tweaks and I got a great, dynamic metal tone.

Rock and roll!

Starting to look good!

This sounds like a great platform, but not something I'm very familiar with.  Care to share any pictures?  We'd love to see it!

Quote from: GeezerB on August 31, 2023, 12:46:52 PMJust bought a loupe... great tip thank you.   I also believe I may have solved my issue! I reflowed all the joints on amp board just in case... and the transistors that were held on by screws I removed and cleaned up the connections.   And cleaned the hell out of the "Mute" switch... could not play too loud last night due to sleeping house but did not hear any popping and sounded good... so I believe my problems were the bad power amp connections combined with the Zener diode in the preamp.   Thanks to the forum... what a feeling.

Glad to hear you got it fixed up!  I always love a happy ending.

Quote from: GeezerB on August 23, 2023, 10:28:32 PMI input a nice clean 1k sine wave, and here is the result from both the preamp out and from the power amp out... both appear to be wonky. 

I guess this tells me at least that the distortion is starting in the preamp section at least?  But it still seems that the power amp should be louder.

I guess I also need to understand the function of Gain and Master...Gain is there for crunch, but doesnt control volume?

First time using this scope, it is really cool to use such a powerful tool for diagnosis, cant wait to use to greater potential and understanding.

Gain is really preamp volume.  The higher you turn up the gain, the more it will saturate into distortion (depending on the amp, this could be setting the gain on 3 or 4, or maybe 5 or 6 before serious distortion kicks in).  The master is the volume control between the preamp and power amp.  This controls the overall volume at the speaker level.

To be clear, turning down the gain will decrease volume as well but it does this in the preamp section and as it is turned down it will decrease volume as well as distortion.

Quote from: Tassieviking on August 04, 2023, 10:34:15 PMAccording to the SUNN BETA service manual:
The Sunn Beta has 1.75v P-P out at the master line output, but each individual channel has only 1.1v P-P at the preamp line output.
Sunn Beta basically has 3 effect loops.
If you made a single channel the output to the power amp is only 1.1v P-P which should be ok, and you don't have to crank the volume pot all the way around.

If anything you might not get enough signal to drive the TPA chip to full power since the Beta figures are peak to peak.

I think it should be OK.  The TPA3116 has gain from 20 to 36db.  I haven't done the math to verify, but I think this should get close.

If you crank up the volume on the clean channel, is there a similar sound?

Quote from: Domin9797 on August 02, 2023, 01:59:54 PMYeah but often shipping costs more than PCB. TPA3116 is good choice too but im not sure if i want PA which cant sound "good" while clipping. I have only 20W speaker so im little bit limited.
I know about his circuits. His MDR will be my distortion channel or at least distortion pedal. Im not sure about 59 Bassman since there arent any sound clips of it. Another idea is his Orange emulator

Personally I don't worry about clipping the power amp.  You can design the preamp in such a way (utilizing diode clipping for instance) that you can't clip the power amp section no matter how hard you drive the front end.