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Mender device for fender twin reverb

5/18/1998 6:19 AM
lou	Mender device for fender twin reverb Greetings everyone,Does any body have an idea how this mender works.A budy is trying to sell me one but I am not sure I want to put it in my "67" twin. I understand it turns the amp in to a channel switching mode between one and two with reverb on both and channel one dirty?! Is it safe-It sound like a good idea if it works and sounds decent. Thanks for any response. Cheers Lou.

5/18/1998 6:19 AM

lou

Mender device for fender twin reverb

Greetings everyone,Does any body have an idea how this mender works.A budy is trying to sell me one but I am not sure I want to put it in my "67" twin. I understand it turns the amp in to a channel switching mode between one and two with reverb on both and channel one dirty?! Is it safe-It sound like a good idea if it works and sounds decent.
Thanks for any response.
Cheers
Lou.

5/18/1998 8:08 AM
GFR	In clean mode, it's your reverb channel sound(totally stock). In overdrive mode, the normal channel is put in series with the reverb channel. Tone controls are independent, not interactive like in a boogie. Distortion is before tone controls. There's a gain preset in the Mender. Reverb is active in both modes. No mods at all to your amp, so it doesn't hurts trying. This is from the review in GP mag, I have never heard one or seen an schematic (anyone's got it?). The sound is reported as not so good, but tone is a matter of taste and I think it would be easier and safer to tweak the Mender to get the tone you want than mess inside a vintage amp. And your amp remains absolutely stock in the process. There's also a Mender II that turns the reverb in/outs into a parallel effects loop with send and return knobs(without losing the reverb). Anyone tried this? GFR

5/18/1998 8:08 AM

GFR

In clean mode, it's your reverb channel sound(totally stock). In overdrive mode, the normal channel is put in series with the reverb channel. Tone controls are independent, not interactive like in a boogie. Distortion is before tone controls. There's a gain preset in the Mender. Reverb is active in both modes. No mods at all to your amp, so it doesn't hurts trying. This is from the review in GP mag, I have never heard one or seen an schematic (anyone's got it?).

The sound is reported as not so good, but tone is a matter of taste and I think it would be easier and safer to tweak the Mender to get the tone you want than mess inside a vintage amp. And your amp remains absolutely stock in the process.

There's also a Mender II that turns the reverb in/outs into a parallel effects loop with send and return knobs(without losing the reverb). Anyone tried this?

GFR

5/18/1998 8:13 AM
Steve M.	Hi Lou, I had one of the Mender devices, actually the Mender I which is the highgain/channel switching module. The Mender II was built to fit into the reverb circuit to add an FX loop. Basically the Mender I cascades the gain stages of the first channel (normal) into the second (reverb or "cool") channel. It also places the EQ after the distortion. From my understanding, the reberb channel is always "on" and the normal channel gets switched in and out of the circuit. As far as being safe, I never had a problem with mine, and it shouldn't hurt the amp. The manufacturer did state that Fender amps were not designed as high gain amps, and therefore there could be unwanted noise. As far as sound, I never really liked the sound of it, I thought the distortion was too fuzzy and had a "buzzsaw" character. That's not to say that you may not like it, give it a try you might like it fine. hope this helps, Steve

5/18/1998 8:13 AM

Steve M.

Hi Lou,

I had one of the Mender devices, actually the Mender I which is the highgain/channel switching module. The Mender II was built to fit into the reverb circuit to add an FX loop.

Basically the Mender I cascades the gain stages of the first channel (normal) into the second (reverb or "cool") channel. It also places the EQ after the distortion. From my understanding, the reberb channel is always "on" and the normal channel gets switched in and out of the circuit.

As far as being safe, I never had a problem with mine, and it shouldn't hurt the amp. The manufacturer did state that Fender amps were not designed as high gain amps, and therefore there could be unwanted noise.

As far as sound, I never really liked the sound of it, I thought the distortion was too fuzzy and had a "buzzsaw" character. That's not to say that you may not like it, give it a try you might like it fine.

hope this helps,

Steve

5/18/1998 11:01 AM
Mark Buckingham	>I had one of the Mender devices, actually >the Mender I which is the >highgain/channel switching module. The >Mender II was built to fit into the reverb >circuit to add an FX loop. I had one as well. It could sound ok... I once had it runing on my '77 twin, with the twin connected to a Sholtz Powersoak. That sounded pretty darn good. With my Strat & lace sensors it had a sound like Clapton's on the 24 nights CD. All that aside, I had a lot of noise with mine. (Part of the fun of high gain...)

5/18/1998 11:01 AM

Mark Buckingham

>I had one of the Mender devices, actually >the Mender I which is the >highgain/channel switching module. The >Mender II was built to fit into the reverb >circuit to add an FX loop.

I had one as well. It could sound ok... I once had it runing on my '77 twin, with the twin connected to a Sholtz Powersoak. That sounded pretty darn good. With my Strat & lace sensors it had a sound like Clapton's on the 24 nights CD.

All that aside, I had a lot of noise with mine. (Part of the fun of high gain...)

5/18/1998 1:05 PM
GFR	Mark, Steve, Does any of you have an schematic for the Mender I? Would you mind posting it to me? In the guitar player review Paul Rivera said that it used 4 gain stages in lead mode, and I can't figure a way to get more than 3 stages from "outside" the amp like the Mender does. Very curious. Also anybody knows if they are still being made (haven't heard of Hicks Electronics for a while)? Thanks, GFR

5/18/1998 1:05 PM

GFR

Mark, Steve,

Does any of you have an schematic for the Mender I? Would you mind posting it to me? In the guitar player review Paul Rivera said that it used 4 gain stages in lead mode, and I can't figure a way to get more than 3 stages from "outside" the amp like the Mender does. Very curious. Also anybody knows if they are still being made (haven't heard of Hicks Electronics for a while)?

Thanks,

GFR

5/18/1998 1:54 PM
Mark Buckingham	GFR- I don't have a schematic... The PCB inside of the unit was glued - trace side down - into the little plastic case. The mender circuit takes all of the tube pins out of the circuit. Since you can do this you end up with little modules like: A (input jack) B (first stage of tube #1) C (tone stack) D (volume control) E (second stage of tube #1) F (first stage of tube #2) G (tone stack) H (volume control) I (second stage of tube #2) I think it may also run more than one plate off of the same plate resistor, so the outputs of the stages could be separated more... A way to get all four stages could work like this: (filtering added to clean up the high gain mess...) A -> B -> filtering -> E -> gain control -> filtering -> F -> C -> D -> E -> back to the vibrato channel circuit

5/18/1998 1:54 PM

Mark Buckingham

GFR-

I don't have a schematic... The PCB inside of the unit was glued - trace side down - into the little plastic case.

The mender circuit takes all of the tube pins out of the circuit. Since you can do this you end up with little modules like:

A (input jack)
B (first stage of tube #1)
C (tone stack)
D (volume control)
E (second stage of tube #1)
F (first stage of tube #2)
G (tone stack)
H (volume control)
I (second stage of tube #2)

I think it may also run more than one plate off of the same plate resistor, so the outputs of the stages could be separated more...

A way to get all four stages could work like this: (filtering added to clean up the high gain mess...)

A -> B -> filtering -> E ->
gain control ->
filtering -> F ->
C -> D -> E ->
back to the vibrato channel circuit

5/19/1998 7:44 AM
GFR	Thanks Mark. There's a litlle detail that we don't have access to B+, only to the plate resistors. And that the plate resistors of the first stages are internaly (inside the amp)connected to the tone stacks, and the tone stacks are internally conected to the volume controls. Also the plate resistor of the normal channel 2nd stage is internally connected to the mixer resistor to the power section and the plate resistor of the rev channel 2nd stage is internally connected to the reverb circuitry. We have: A) normal input jack; B) normal 1st plate resistor->tone->vol, plate resistor end; C) normal 1st cathode res+cap; D) normal 1st plate resistor->tone->vol, vol control end; E) normal 2nd plate resistor->power F) normal 2nd cathode res+cap; G) rev input jack; H) rev 1st plate resistor->tone->vol, plate resistor end; I) rev 1st cathode res+cap; J) rev 1st plate resistor->tone->vol, vol control end; K) rev 2nd plate resistor->rev; F) normal 2nd cathode res+cap (shared); L) ground. That's all the points we have access through the amps sockets and the ground wire screwed to the cabinet. We don't need to care about the cathodes cause we have access to ground, so I'll look only at grids and plates. We have also two tubes and need to connect them to the above points in such a way that: 1) volume and tone are independent of the rev channel alone - so we can't use point J; 2) the tone and vol are after distortion, and we have reverb - so point D goes to grid(V2B); 3) point F can't be used because it would send a non-reverbered signal in parallel with the rev sound, and probably out of phase. With this constraints I can imagine a three stage configuration: 1)Point G goes to grid(V2A), point H to plate(V2A) just as in clean mode. Point H goes also to a cap and a resistive divider (the gain control). Point J is left unconnected; 2)The resistive divider goes to grid(V1A), point B goes to plate(V1A); 3)Point D goes to grid(V2B) and point K to plate(V2B); 4)Caps on some places to cut highs. There's one stage left (V1B) but I have already used points B,H and K and can't use point E, so there's no available plate load unless I share a plate load. Sharing a plate load would act like summing the currents of both stages and to avoid phase problems the only way left to use all triodes is to have two triodes in parallel in one of the stages. But this would give me effectively three stages of gain. Of course, Mr. Rivera may have called this as four stages in his review. There's also the possibility of placing a big electrolytic cap from point E to ground and use it as a low B+ source (200V or less), so I can connect an aditional plate resistor to this point and have little leakage to the power section. Can you measure the plate and cathode voltages without 'ungluing' the board? This can give a hint on what's happening inside the mender. GFR

5/19/1998 7:44 AM

GFR

Thanks Mark.

There's a litlle detail that we don't have access to B+, only to the plate resistors. And that the plate resistors of the first stages are internaly (inside the amp)connected to the tone stacks, and the tone stacks are internally conected to the volume controls. Also the plate resistor of the normal channel 2nd stage is internally connected to the mixer resistor to the power section and the plate resistor of the rev channel 2nd stage is internally connected to the reverb circuitry.

We have:

A) normal input jack;
B) normal 1st plate resistor->tone->vol, plate resistor end;
C) normal 1st cathode res+cap;
D) normal 1st plate resistor->tone->vol, vol control end;
E) normal 2nd plate resistor->power
F) normal 2nd cathode res+cap;
G) rev input jack;
H) rev 1st plate resistor->tone->vol, plate resistor end;
I) rev 1st cathode res+cap;
J) rev 1st plate resistor->tone->vol, vol control end;
K) rev 2nd plate resistor->rev;
F) normal 2nd cathode res+cap (shared);
L) ground.

That's all the points we have access through the amps sockets and the ground wire screwed to the cabinet. We don't need to care about the cathodes cause we have access to ground, so I'll look only at grids and plates. We have also two tubes and need to connect them to the above points in such a way that:
1) volume and tone are independent of the rev channel alone - so we can't use point J;
2) the tone and vol are after distortion, and we have reverb - so point D goes to grid(V2B);
3) point F can't be used because it would send a non-reverbered signal in parallel with the rev sound, and probably out of phase.

With this constraints I can imagine a three stage configuration:
1)Point G goes to grid(V2A), point H to plate(V2A) just as in clean mode. Point H goes also to a cap and a resistive divider (the gain control). Point J is left unconnected;
2)The resistive divider goes to grid(V1A), point B goes to plate(V1A);
3)Point D goes to grid(V2B) and point K to plate(V2B);
4)Caps on some places to cut highs.

There's one stage left (V1B) but I have already used points B,H and K and can't use point E, so there's no available plate load unless I share a plate load. Sharing a plate load would act like summing the currents of both stages and to avoid phase problems the only way left to use all triodes is to have two triodes in parallel in one of the stages. But this would give me effectively three stages of gain.

Of course, Mr. Rivera may have called this as four stages in his review.

There's also the possibility of placing a big electrolytic cap from point E to ground and use it as a low B+ source (200V or less), so I can connect an aditional plate resistor to this point and have little leakage to the power section.

Can you measure the plate and cathode voltages without 'ungluing' the board? This can give a hint on what's happening inside the mender.

GFR

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