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Chopped Wurli Amp Issue

Started by Wesley, January 14, 2023, 07:02:33 PM

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Wesley

Hey everyone,
I'm working on chopping a student Wurlitzer 214 and was almost done but I ran into an issue. Got everything out back together but now the output is crackling really bad. It wasn't messed up before the chop so I must have done something wrong. I did put an 8omh resistor on the speaker wires. Does anyone have advice on how to fix this before I have to go and buy a new amp? Thanks!

Here's a video of the issue:
https://youtube.com/shorts/3_GLNDtlbhM?feature=share

Edit: I found a good deal on an original but good condition amp so I'm just going to replace it. Hopefully that fixes the issue.

Wesley

Update:
So I got a new (old) amp installed and the terrible cracking firework noises are gone but the output on the aux out and amp out are too hot. The aux is usable and only sort of distorted but the amp out is way too distorted for general use. My guess is that I need a resistor on the speaker out (I'm not using speakers) but I don't know where the speaker pins on the amp are because there aren't any labeled. Can anyone confirm my theory of the amp resistance or have any other ideas why the sound is too driven? It sounds like it was gained up way too much and is distorting/clipping. I have checked the scrolling wheels on the the amp and set them as low as possible. Thanks anyone who has advice on this.

Electrickey


Wesley

Yes I guess the headphone out is what I was calling amp out.

I just discovered though, that the aux out has a good line level output that's not distorted if I put a dummy 1/4" in the headphone out. I'm guessing this takes care of the amp resistance issue. I'm not sure why the aux out is line level (it can drive headphones with plenty of volume), but it is working well for what I need.

The headphone out is still totally distorted and is not affected by putting a dummy jack in the aux out.
I'm just going to use the aux out for now. Not a complete fix but fixed enough. Unless someone has advice on how to actually fix the issue in which case I will fix it.

Electrickey

The headphone out on my 200A and it's the original amp/electronics no mods, is somewhat distorted as well with some hum audible and is only one side of a stereo (left) field.

The AUX-out does not drive headphones for the unit I have. I used a Sony MDR-7506 studio set.

These instruments were not meant to be high fidelity and I've heard the electronics are not well designed. But then that's part of the character which is why it's been left stock. A 50 year old instrument will pale in comparison sonically to today's and we've become used to higher fidelity forgetting what the Wurli's limitations are.

Reason why amps for these models are being redesigned and sold as upgrades for those wanting a clearer performance.

When using it for concerts a dummy jack is placed in the headphone out to mute the speakers.


pianotuner steveo

There is a trim pot on the amp board, does turning this down lower the distortion?
Are you sure you don't have a bad output transistor?
I'm confused about why you were adding an 8 ohm resistor to the output.

True headphone outs should be about 32 ohms. (on modern equipment)
1960 Wurlitzer model 700 EP
1968 Gibson G101 Combo organ
1975 Rhodes Piano Bass
1979 Wurlitzer 206A EP
1980 Wurlitzer 270 Butterfly Grand
2009 73A Rhodes Mark 7
2009 Korg SV-1 73
2017 Yamaha P255
2020 Kawai CA99
....and a few guitars...

pianotuner steveo

Sound only going to one side of the headphones is caused by using stereo headphones in the mono Jack. Either use mono headphones, or replace the mono Jack with a stereo Jack, and be sure to connect the + audio wire to both + terminals.
1960 Wurlitzer model 700 EP
1968 Gibson G101 Combo organ
1975 Rhodes Piano Bass
1979 Wurlitzer 206A EP
1980 Wurlitzer 270 Butterfly Grand
2009 73A Rhodes Mark 7
2009 Korg SV-1 73
2017 Yamaha P255
2020 Kawai CA99
....and a few guitars...

DocWurly

#7
Are we talking about a 214 or a 214A here?

I'm assuming this is a 214.

You can't use a headphone out for a line level. You need to get clear on which is which.

A 214 needs a few caps and resistors added to approximate a 200.

If we are talking about a 214A --ah, maybe we are-- it's a completely different issue, probably involving blown 2 amp fuses and further confusion about aux vs headphone outs.

You can't put a dummy jack in the aux to use the headphone out. It only works the other way around.

Either way, you should be consulting schematics. And taking safety precautions.