Danelectro - Tuna Melt Tremolo

A forum devoted to mod, tips and suggestions for upgrading and rehousing your VERY CHEAP commercial stompbox to near boutique excellence.
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angelodp
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Post by angelodp »

Has anyone put a volume pot on this pedal?

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frankus
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Post by frankus »

Hello peeps - long time lurker :)

I've decided to rehouse one of my tuna melts in a 1590a (as is the current fashion).

Rather easily done by cutting a lug off the main pcb, which only housed one of the mounted potentiometers (ditched the original power-board long ago).

Drill a few extra holes further into the trace wire it in.. put a big fat alpha pot there and get one of those fat fullertone knobs to control the rewired pot - lovely... but

the rewired pot was for the depth control rather than the speed control. The depth control gets a nice healthy big pot... which sits front and center on a 1590a?

At first I thought "no this must be the speed control" but for soft settings it'd be cooler to swell the depth... leaving only the hard setting where I reckoned speed would be of the essence.

So I came up with an idea to switch the pot usage ... when the soft option is tripped - after all the pots are both 100k how hard can it be?

Turns out - to my rather limited brain - rather difficult, either a 7pdt or relays - neither of which scream 1590a enclosure... so I thought a while (actually I gave up and the idea came to, but anyway)... if I supplied a voltage to each potentiometer and had it power an LED that drove an LDR that controlled the speed and depth then a dpdt switch could swap the knobs designation easily.

Does anyone foresee woes or great troubles with this? Either power consumption or sweep weirdness on the pots or stuff? Any other pointers - ta :D

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frankus
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Post by frankus »

Okay.. maybe I'm being less than clear - it's a known flaw. :mrgreen:

Image

The idea is to replace vr101 and vr102 in Clay Jones' fine schematic with 100k resistors across 1 and 3 lugs.
an LDR from vr101 lug 1 to R111 (replacing lug2)
an LDR from vr102 lug 1 to R117 (replacing lug2)
the LDRs are each connected to an LED fed through a DPDT switch
each LED's intensity is controlled by a potentiometer

when the switch is thrown the potentiometers controlling the LEDs are swapped over.

The knobs on the potentiometers are non-symetrical - the dominant one being a Ribby 35mm (for foot control - mounted centrally) the lesser being a 6mm alpha pot for minor tweakage.

This allows either swells in the effect or increases in the speed to be controlled interactively during the play - like an expression pedal not as ostentatious (outwardly at least).

Is that clearer? Anyone foresee any issues - or got any advice.

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frankus
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Post by frankus »

... or can I simply use transistors set to a max of unity gain?

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frankus
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Post by frankus »

Just out of curiousity why has noone answered this thread?

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Dr Tony Balls
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Post by Dr Tony Balls »

frankus wrote:Just out of curiousity why has noone answered this thread?

I really have a hard time understanding what you're saying. Im sure others do as well. For example:

frankus wrote:Hello peeps - long time lurker :)

I've decided to rehouse one of my tuna melts in a 1590a (as is the current fashion).

Rather easily done by cutting a lug off the main pcb, which only housed one of the mounted potentiometers (ditched the original power-board long ago). Dont know what this means. What lug? What pot? What is the power board and why does it matter here?

Drill a few extra holes further into the trace wire it in.. put a big fat alpha pot there and get one of those fat fullertone knobs to control the rewired pot - lovely... but Wire what in?

the rewired pot was for the depth control rather than the speed control. The depth control gets a nice healthy big pot... which sits front and center on a 1590a? I dont understand the question. What does pot size matter?

After this the remaining post made no sense to me what so ever.

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frankus
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Post by frankus »

ok, thank you for replying,

I can now see how my post is vague, ill-thought-out and littered with confusing phrases.

I'll rephrase what I've said to be clearer, where I still fail - I'm sorry, I'm using this project to improve my understanding, I'll do my best to be clearer.

The size and shape of the tuna-melt PCB is such that it can be fitted into a 1590a PCB by cutting off a 1cm x 1cm chunk on one side. This chunk of PCB is only used to connect and anchor one of the surface mounted pots (the depth control). So cutting off the extra lump of PCB means the PCB will fit nicely into a 1590A.

Image

You can see the piece on the left over the battery.

After cutting off the lump of PCB, 3 holes can be drilled into the remaining trace (and the etch protect scraped off) to allow up an off-board pot to be wired to the PCB. The hard/soft switch and speed potentiometer (both mounted on the PCB) could stay there ... but it got me thinking about the knob layout.

I figured a Ribby knob would allow for foot control, so when I've said "large pot" I really meant "large knob".

Image

There's not enough room for both speed and depth controls to get large knobs so I wanted to explore the idea of being able to swap the function of the pots around - if I want the speed to be foot controlled I set a toggle switch set one way.. if I want the depth control to be foot controlled I set the toggle switch the other way.

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frankus
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Post by frankus »

:?

The absence of love is the most abject pain...

I'll just get on with it, then...

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Post by Camaro guy »

I've been running a Danelectro Tuna Melt Tremolo between my Rhodes and Princeton Chorus amp and really like the sound, actually sounds better to me than some more expensive tremolo boxes, in fact. After about 6 months, I had a problem where the foot switch no longer turned it on and off (stayed on), but the effect itself worked just fine. I figured that it was the momentary DPDT contact switch, so I replaced it with a full-size switch and that solved the problem. For about 5 days. Back to the same issue. Now I can't get it to turn on except by plugging and unplugging the 9V cable multiple times until I get lucky.

I could re-house the pedal, but by the time I bought the true bypass switch, enclosure, pots, etc., it would be getting up close to the cost of a replacement pedal. I hate to throw away a pedal that I like and that basically works, except for the on-off part. I have two questions:

1. Is the entire tremolo circuit on the top board of this pedal? In other words, is the only function of the bottom board to provide buffered input, the in, out and 9V jacks and the on-off switch?

2. Has anyone seen this kind of behavior in a Danelectro pedal before? If it's just swapping out a defective component, that would actually be my preference instead of re-housing.

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Post by MoonWatcher »

I think I've had 3 Tuna Melts now. I destroyed a pair of them when attempting the rehousing.

The Dano minis put the in & out jacks, power jack - stuff like that on the smaller of the two boards. The main board has the pots, toggle in the case of the TM, momentary switch, LED, actual switching logic, and circuit proper on that main board.

Depending on the model, some may have stuff on the "auxillary board" for op amp biasing and things like that. I think such is the case with the Tuna Melt. I had a French Toast that I rehoused, and it didn't need the bias stuff. That meant that the connecting ribbon cable was different, too.

I've never had an issue with the logic switching or the "paddle momentary" that seems to be used on a lot of the Dano stuff.

With the re-housing, I've always had issues with pulling the stock pots off and hooking up external ones. The pot housing tabs form ground bridges that have to be re-connected when they are removed. And the pins or lugs of the pots simply wrap around the edge of the pcb and are a pain to replace with wires to off-board pots. I think it might be better to leave the stock pots in place and just unsolder the lugs, and try to come up with some reinforced method to keep the wires from falling off.

I have also had problems with trying to reuse the "auxilliary board" and having to deal with the ribbon cable. I think other guys who've done rehouses just ditch that board and build their own power supply, bias supply, and in and out connections.

I think that Clay Jones did a hand drawn schematic of the Tuna Melt, but a lot of component values were left out. If someone could simply wrap that part up, it would be easy enough to knock out a Tuna Melt on veroboard or something.

Since I have one final working Tuna Melt, I've wanted to do that myself, but have yet to put aside the time for it. It's not an overly complicated circuit either. Possibly the most important part is getting the specs for the LDR. Well, the components are tiny, too. But I'd think the resistor values and such are straightforward, and the stock bypassing parts could all be dropped as well.

At one point, I was honestly thinking of just stuffing the stock TM in a box big enough that I could just graft wires into all the existing parts of the pedal, just cutting parts of the plastic enclosure away as needed. It would look stupid inside the box, but the TM internals wouldn't fall apart in the process.

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mrkgtr49
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Post by mrkgtr49 »

First off, I love my Tuna Melt. Got it when the model first came out, and have used the s**t out of it over the years. But the years have taken their toll, and now I want to re-house it. I've built a few pedal kits and even figured out how to put a booster unit that was intended to go into a guitar in a box so I could use it with more than one guitar.
The question I have is: what are the pot values for the speed and depth controls? I know I could unsolder them and just read them, but before I start tearing the thing apart I want to get my ducks in a row, parts wise.
So: has anyone done this, and what pots did you use?

Thanks Gang!

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Post by tabbycat »

hi mrkgtr49, and welcome to fsb.

tuna melt is a nice trem poorly housed. a lot of re-housing about...

http://www.thegearpage.net/board/index. ... de.152311/
http://www.thegearpage.net/board/index. ... -2.202746/

https://tetsuoelectronics.wordpress.com ... rehousing/

Re: Re-house or fix a Danelectro Tuna Melt Tremolo?
https://www.freestompboxes.org/viewtopic ... 10#p225610

though, as mentioned in the last thread...
MoonWatcher wrote:With the re-housing, I've always had issues with pulling the stock pots off and hooking up external ones. The pot housing tabs form ground bridges that have to be re-connected when they are removed. And the pins or lugs of the pots simply wrap around the edge of the pcb and are a pain to replace with wires to off-board pots. I think it might be better to leave the stock pots in place and just unsolder the lugs, and try to come up with some reinforced method to keep the wires from falling off.

I have also had problems with trying to reuse the "auxilliary board" and having to deal with the ribbon cable. I think other guys who've done rehouses just ditch that board and build their own power supply, bias supply, and in and out connections.

I think that Clay Jones did a hand drawn schematic of the Tuna Melt, but a lot of component values were left out. If someone could simply wrap that part up, it would be easy enough to knock out a Tuna Melt on veroboard or something.
the incomplete hand-drawn clay jones tuna melt schemtaic referred to is in the second tgp post above.

if you can identify the missing values (a basic digital multimeter useful, though you may be able to read off capacitor codes/ resistor colour codes) you may find it far quicker and easier to make a vero from scratch than try to unscramble an egg. you could then sell your original tuna melt on to generate funds to buy something else.

rehoused tuna melt and new pedal. win win.

if you are unfamiliar with schematics or converting a schematic to vero, post the values here and others may be able to help join the dots. a vero tuna melt would be a nice project to have here.

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