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Author Topic: Fender Ultimate Chorus: loose tabs on the speaker housing + 2 quick questions  (Read 2838 times)

Stefan

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Fender Ultimate Chorus solid state amp from 1990’s (130W, 240V).

Could someone please shed some light on these, probably very easy to answer questions.

1. What is the role of the tabs/lugs connecting the words from the amp to the speaker housing? 

(see links to photos) The tabs on my Fender Ultimate Chorus are both loose, and can easily be moved/removed. Not sure why it was built this way — given everything else on the amp is well made  (and yes, I will dust).





Are these tabs an electrical fitting or a mechanical fitting? (My guess is electrical, as the pos/neg terminals of the cables sit on a metal clip, which then connects to the metal speaker housing.) 

How important is it the tabs are a tight/solid fit? Will they vibrate off? Cause distortion if even a bit loose? If it is important, could I solder them in place; or is a better option to drill a hole in the speaker housing and bolt/rivet them on?


2. Reverb cables to the reverb box, does it matter which they they go on?
Are the red and black cables on the reverb box (RCA connectors) reversible? That is, does the circuitry mind which way they are plugged in? Tried both ways and it does not seem to make any difference. (I think the term for this is ‘polarity’.) Just want to be sure.


3. Recommendation please for amp servicing near Geelong, Victoria Australia. 

In case it ever comes to this. (Amp sounds very good, had it for a while, but want to make sure I'm getting the best out of it.)





Thanks in advance.

Stefan
West coast of Vict
Australia

DrGonz78

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I could not see the pictures you are referring to... However I do see the links...
https://stefancarey.zenfolio.com/p553178115/hF606202E#hf606202e
https://stefancarey.zenfolio.com/p553178115/hF6062034#hf6062034

2. Reverb cables to the reverb box, does it matter which they they go on?
Are the red and black cables on the reverb box (RCA connectors) reversible? That is, does the circuitry mind which way they are plugged in? Tried both ways and it does not seem to make any difference. (I think the term for this is ‘polarity’.) Just want to be sure.

Each RCA cable has a signal and ground feeding signal to and from the reverb tank. Lets guess that the RED is sending signal IN (input on the reverb tank) and BLACK is sending signal (output on the reverb tank) back to the circuit in the amp. Drive circuit (I think is what it's called) sends to the input of the reverb tank and Recovery circuit (again this is what I call it) is the return signal from the output of the reverb tank.

Now as far as troubleshooting if you have tried cables both possible configurations then it appears, at a minimum, that the recovery circuit is not working.

“A person who never made a mistake never tried anything new.” -Albert Einstein

Stefan

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DrGonz78


Thank you so much for your quick response (and posting the links).

I had no idea RCA worked that way, so thanks for the excellent explanation.


Reverb | I probably was not clear enough, but the reverb works fine -- it was the order of the cables I was unsure about (ie does it matter which RCA jack you plug the red/black in.). From what you said it sounds like no. Any order is fine.

Photos | I found out how to upload images by searching for image upload, and it worked. Just use the attachment function.

Thanks again.

Stefan











« Last Edit: February 12, 2021, 06:45:09 PM by Stefan »

g1

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It's not clear to me which part of the speaker terminals you mean.
The wires coming from the amp have spade lug connectors on them.  That is so you can disconnect them without soldering when you need to remove the chassis or speakers.  If that fit is loose, you can carefully squeeze with  pliers to make it more of a snug fit.

The reverb will work either way with this amp, but there is a correct way.  The ground schemes and impedances are different for each end. When connected the correct way, it will perform better in terms of sound and also for noise and hum rejection.
Disconnect the cables at the reverb tank, turn up the reverb level a bit and touch the cable tip.  Try each cable (red & black).  One of them will cause hum when you touch it.  That one is the 'return'.
  Look closely at the jacks on the tank.  Connect the 'return' cable to the tank jack that is labelled 'out'.

Stefan

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DrGOnz78

Superb explanation of what to do the reverb tank connections -- so thank you. As there are no markings as to 'in' and 'out' etc on the tank (see photos), I'll try listening with different reverb settings. Or better still I'll see if I can find a circuit diagram of the reverb tank.

Also appreciated is the explanation of the lugs and what they do. To help explain my question more clearly, I've added a new photo to try to make my explanation a little clearer.

thanks

Stefan



g1

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Ok, I see that you mean where the fiber board is riveted to the speaker frame.  On the other one you can see it has been glued in place.
They are usually able to pivot a bit but should not come off.  You can either re-rivet or use a nut and bolt to secure.

On the reverb tank, you can see how there is lettering stamped in to the top (Accutronics etc.).  The jack labeling should be stamped like that near the jacks.
Also you can measure the resistance at each jack.  For this particular model tank, one end should be around 100 ohms and the other end around 200.  The higher reading of the 2 is the 'out' jack.
« Last Edit: February 13, 2021, 02:01:19 PM by g1 »

Stefan

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Fantastic information, thanks for taking the time to answer my questions.

cheers

Stefan