f100 combo....reverb stopped working

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Tmuggie

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Hi,
I have an f100 combo and the reverb stopped working....any ideas?
Thanks
 
my f100 also has been experiencing some problems, mainly with tone and channel volumes... not reverb...still
 
Perhaps put a patch cable in the loop to bring it "always on", and the mix control at full. (Rkorn). Or have a look at the relays for the channels. My f-30 had a problem for a while with the mute switch, which was "stuck" in between the mute and normal position and "drained/dropped" the sound. Switching it back and forth cleaned it up and works ok.


The reverb? Well if the tank is busted you need to try another tank or the footswitch or relat maybe the culprit. Or a busted cap or something to bring it in the circuit. If you don't have any luck with those I'll e-mail you schematics for your tech to have a look at.
 
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.
 
I was thinking of taking the amp out of the combo and check everything. I'm sure that some components have lost its juice.
I believe it is normal that every amp needs some check ups once in a while... components don't last forever.
Has anyone ever done this? I know the amp doesn't sound like it once did!
 
Hey Rkorn -

If by components you mean the tubes, those would be the first place to go. If you haven't done that, this is where you start.

As for the components inside the chassis, there is nothing used in the amp that is designed or spec'd out that should last any less than 20 years with normal use and potentially a lifetime besides failures.

Maybe it's just Boogie, but we don't use parts that have a 5 or ten year lifespan. Every amp we make uses the same parts and every amp we make is an amp we build to last for decades to a lifetime.

Everyone has their opinions about filter caps (which is largely generated by people's suggestions for re-capping old and much more vintage amps that didn't use the longest lasting filtering parts) but the bottom line is, we can't suggest that there's any components inside the amp that will need to be changed in even the very first F100 ever built, even if the thing was played for 5 hours a day for 10 years.

Probably stating the obvious but if the tubes haven't been checked, thats first. If that doesn't bring the thing back to original glory (and you're using Boogie tubes), it may be time for the amp to go to a tech to look for a failure of some sort.

Hope this helps and best of luck getting it back to 100%. Give a call to the factory and a PM if you'd like as well.

Cheers,

Authorized Boogie
 
Tubes were changed already. It was the first thing we thought about.
I thought also about sending it to you, but being from Portugal, i'm afraid we'll be without an amp for months.

I'll send you a PM to see what can be done about it!
 
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.

Hey thanks for the info....I haven't been on here in a while, sorry for the late response.
How does a reverb tank go bad by the way? I do recall moving it a few weeks before it stopped working. I don't recall anything out of the ordinary happening though.
 
Reverb tanks have generally at least 2 (and in the case of Boogie tanks, 3) springs suspended from 'posts' on each end of the tank. Sometimes the posts will break and the spring then lays across the other springs causing problems.

Sometimes the wires going into the tank and connected to the transducers will break away from their connection points. Either of these town things can occur when moving the amp. The final straw may not have as much to do with the one move but the cumulative effect of all the moves and then a final failure.

The other likely culprit for reverb issues, although rarely a full cutout of sound, is build-up and contamination on the jacks or plugs of the reverb cables where they plug into the amps. It's a good idea to at least spray the jacks with contact cleaner every once and a while, especially if you live in a more humid environment. If this is an issue, it usually manifests as crackling or sometimes as distortion being added to the sound only when reverb is on.

Hope this helps.
 
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
 
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?
 
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.
 
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...
 
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.

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.
 
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...
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.
 
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.

Muggie - If the footswitch is unplugged, the reverb is by default, on. If no footswitch plugged in and reverb turned up and still no reverb, the problem is likely to be internal in the amp. Reverb IC chip or Muting Transistors in the reverb circuit.
 
Ok. I haven't had a chance to check the resistance readings yet but if I do and I determine that the tank is ok, I could replace the chips and or transistors. I have a fair amount of electronic experience, soldering and what not. Can I determine which things I need to replace by looking at the board...is anything labeled?...or do I need to get a schematic?...or could you point out the likely suspects?
 

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