Authorized Boogie said:Muggie -
In the F100, if the reverb goes out, it is almost always going to be something having gone bad with the tank. Possibly cables but more likely to be the tank and there are no tubes in the reverb circuit of the F series amp so this makes troubleshooting a bit easier.
If the reverb stopped working after you have recently moved the amp (taken to a gig or an amp that fell over or went for a rough ride), this might be a hint that the tank has been damaged and needs to be replaced to get the reverb working again.
If the tank is bad, its important to note that not any old tank will work. Replacements MUST match the reverb circuit in use and the best way to get the right one is to order from the Mesa factory. Mesa often has proprietary reverb circuits and tanks themselves so its important to make sure you get the right one.
Giorikas - as for your issues, there's not a lot of information to go on but tube troubleshooting would be the first place to start for issues like you've described.
Hope this helps. Let us know how it goes what it is when you get it fixed.
Tmuggie said:Hi,
I took the tank out and looked it over, it looks ok...checked the connections and they seem fine. I took the foot pedal out of the mix to eliminate that. I tried plugging in the rca jacks in backwards than what they were and I started picking up a radio station! Reverb still not working. Should I try a resistance test on the tank leads?...and if so, what should the reading be?
Thanks
Tmuggie said:I know this off topic but I have also been fooling around with the preamp tubes and I have a question about WHEN exactly is a tube considered microphonic? If I turn the amp on and turn it to channel 2, turn the gain up to ten and then start turning the level up it starts getting squealy around 3. That number gets higher as I back off the gain. Should you be able to turn the gain and the volume up to max and not get any squeal?
Authorized Boogie said:Tmuggie said:Hi,
I took the tank out and looked it over, it looks ok...checked the connections and they seem fine. I took the foot pedal out of the mix to eliminate that. I tried plugging in the rca jacks in backwards than what they were and I started picking up a radio station! Reverb still not working. Should I try a resistance test on the tank leads?...and if so, what should the reading be?
Thanks
On an F100 reverb circuit/tank, the Shielded Lead (most likely a black wire in this case) should read approximately 200 ohms across the tip and shield of the plug end.
The input lead (white wire) should read approximately 28 ohms if connecting across the shield/ground of the Shielded (black) cable and the tip of the white cable.
If the tank reads fine with the above test, the problem may either be a muting transistor that turns the reverb on/off or a muting transistor that mute the reverb briefly when channel switching. Beyond that it's possible the reverb IC chip internally is bad.
If it is any of these latter three things, you'll need to take the amp for authorized repair as this is not necessarily user serviceable.
Thanks for the information and links. You are/have been a big help! I think I will post this in the tube section as there is always a lot of talk about microphonic tubes.Authorized Boogie said:Tmuggie said:I know this off topic but I have also been fooling around with the preamp tubes and I have a question about WHEN exactly is a tube considered microphonic? If I turn the amp on and turn it to channel 2, turn the gain up to ten and then start turning the level up it starts getting squealy around 3. That number gets higher as I back off the gain. Should you be able to turn the gain and the volume up to max and not get any squeal?
This is an extensive subject and one best learned by a considerable amount of reading and video watching, both here on the forums and at Mesa's website.
The short answer is no - the amp is NOT designed so you can turn everything up and not have microphonics. Because ALL preamp tubes vary in gain, stability and microphonics and because all circuits vary in how much gain, high frequencies and other circuit specifics are run through the preamp tubes, all these variables along with extreme settings cause at least some level of microphonics with preamp tubes. The key is manageable microphonics based on how the circuit is designed and how the amp is used.
Here's a few things to watch and a few things to read from the Mesa site that may help you with better perspective:
http://mesaboogie.com/news/2010/11/mesa-amplifier-tube-troubleshooting/
http://www.mesaboogie.com/US/Dealers/FAQs/faqs.html#diagpre
http://www.mesaboogie.com/US/Dealers/FAQs/faqs.html#TN-Micro
Stay tuned for more detailed videos in the future on the subject but hopefully this and other research will get you started understanding the somewhat vast subject of preamp tube variability...
Ok...so a question that occurred to me was....Could the foot switch cause the reverb not to work...even if it is not plugged in, by way of turrning the reverb off and then unplugging the foot switch? I have had some issues with the footswitch in the past. The plug that plugs into the foot switch is very touchy.
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