Finally got my Ampeg M-12 all straight.....except for the Trem.
I used the circuit from the schematic. The Intensity was real weak. You had to turn it to 3 O'clock to get signal. The speed was also weak, and fast.
I decreased the Intensity Pot to 500k and increased the .05 cap (the one between the two 120k resistors) to a .1. The Trem is pretty much non-existent now. I am obviously approaching this problem the wrong way.
So what would be the correct solution to my Trem problems.?
Thank You
http://www.unofficialampeg.com/
Tremolo Help
Moderators: pompeiisneaks, Colossal
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Cliff Schecht
- Posts: 2629
- Joined: Wed Dec 30, 2009 7:32 am
- Location: Austin
- Contact:
Re: Tremolo Help
Tbh it sounds like a weak tube or a wrong value. Have you verified by voltmeter that all values are correct? Does tugging on wires affect anything? Are voltages where thy should be? Does an oscope show the oscillator is working? If you don't have a scope then set the speed on min and use your DVM set for ac.
Pics might help too.
Pics might help too.
Cliff Schecht - Circuit P.I.
Re: Tremolo Help
put a VAC meter on where you have the trem injected into, and turn the speed to about 1/2-way (or more) and the depth to max and see what the VAC is. Ideally the pp trem swing should be nearly 2 x about what that stage's tube bias voltage is. If it is, then try cooling the output tube bias a bit. Or if it isn't, then look in your trem circuit for where/why the trem voltage isn't swinging far enough (by looking at the voltages).
He who dies with the most tubes... wins
Re: Tremolo Help
OK....I will try this stuff.
But forgive me here.....do I need some sort of signal going into the amp.?
I have a scope, but I do not have any kind of signal generator other than a guitar.
Thanks
But forgive me here.....do I need some sort of signal going into the amp.?
I have a scope, but I do not have any kind of signal generator other than a guitar.
Thanks
Re: Tremolo Help
To measure the VAC just use your meter, and twiddle with the depth and speed pots until it (the VAC) registers. The trem voltages swings won't register on the VACmeter if its going too slow
He who dies with the most tubes... wins
Re: Tremolo Help
A weak tube will not oscillate. You need a good strong tube for this. It could be something else, as well. Also, you really need a 12AX7 or maybe 5751. A 6SL7 should work. Not sure what you are working with. Internal plate resistance is too low on most other tubes to trigger the oscillation.
Re: Tremolo Help
I used an old PA Head that ran the same number of Octal tubes as the schem for this Ampeg, so that is why I chose this circuit. It uses the 6SL7, so I am stuck with that. I will roll a few tubes to make sure, and take some of those volt measurements ASAP.Phil_S wrote:A weak tube will not oscillate. You need a good strong tube for this. It could be something else, as well. Also, you really need a 12AX7 or maybe 5751. A 6SL7 should work. Not sure what you are working with. Internal plate resistance is too low on most other tubes to trigger the oscillation.
Thank You
Re: Tremolo Help
Still working on this.Cliff Schecht wrote:Tbh it sounds like a weak tube or a wrong value. Have you verified by voltmeter that all values are correct? Does tugging on wires affect anything? Are voltages where thy should be? Does an oscope show the oscillator is working? If you don't have a scope then set the speed on min and use your DVM set for ac.
Pics might help too.
There are no voltages listed on any schematic for this amp.
I will take some pics.
Thanks
-
Cliff Schecht
- Posts: 2629
- Joined: Wed Dec 30, 2009 7:32 am
- Location: Austin
- Contact:
Re: Tremolo Help
Voltages should be somewhat obvious really. Plates should have maybe 100 or so Volts, grids should be slightly more negative than the cathodes.
Cliff Schecht - Circuit P.I.
Re: Tremolo Help
Yeah, in that respect I guess all seems "normal".
Plates are 228
Grids are 0 with no guitar.
The cats are about 3.2
There is some Trem but it is faint and real fast.
I was wondering if, in a "normal" situation", the component changes I made would have helped, or did I get it back wards.
Thanks
Plates are 228
Grids are 0 with no guitar.
The cats are about 3.2
There is some Trem but it is faint and real fast.
I was wondering if, in a "normal" situation", the component changes I made would have helped, or did I get it back wards.
Thanks
Re: Tremolo Help
One More Time......
Just wanted to thank everybody. Got it working well. Made some big changes (component value wise) to the voltage divider that makes up the Intensity circuit. Now I have controllable Trem at desirable "speeds".
Kind of a bizarre Tremolo Foot Switch problem. I got some mono (tip and sleeve only) foot switches from CE Dist. I only tried one, but it turns on the Trem regardless of the position of the switch. The switch is good, I checked it....it does turn on and off. Seems like the length of the plug is JUST long enough to short the circuit to ground all by itself. Tried a random "dummy" plug and the Trem does not come om by itself. So looks like I will just cut that plug off the foot switch and install a new plug that will not short the jack to ground when inserted. Did I explain that clearly......?
Thanks Again
I Appreciate It
Just wanted to thank everybody. Got it working well. Made some big changes (component value wise) to the voltage divider that makes up the Intensity circuit. Now I have controllable Trem at desirable "speeds".
Kind of a bizarre Tremolo Foot Switch problem. I got some mono (tip and sleeve only) foot switches from CE Dist. I only tried one, but it turns on the Trem regardless of the position of the switch. The switch is good, I checked it....it does turn on and off. Seems like the length of the plug is JUST long enough to short the circuit to ground all by itself. Tried a random "dummy" plug and the Trem does not come om by itself. So looks like I will just cut that plug off the foot switch and install a new plug that will not short the jack to ground when inserted. Did I explain that clearly......?
Thanks Again
I Appreciate It