Clavinet E7

[craptical]

The Clavinet always been noisy.

I'm also an E7 owner, and have tried Williams-ish mods on my clav. The difference wasn't dramatic (enough for me to notice) on my E7, but I modded a few friends D6's with positive results. The mods included a metal box for the amp on one of them. You could also get humbuckers from one of the Clav sites IIRC. Still, what's bugging me the most is, why you can't get rid of more of the HISSSSSSSSSS.... 

/Dave

 

[once a roadie]

hey -

I just plugged 16 v AC into my clav E7 power input!  SMOKE show.  (I know this was stupid...had an adapter for a stomp box and I did not look close enough)

I took the PCB out and it looks like I fried the BC238, 8.2 V zener and the 1.8k resistor (probably)...anything else I should be aware of here...recomended replacement parts, etc...?

thanks

 

[tommypiper]

Dave, some transistors become hissy when they are hit with momentary reverse voltage.  I don't know if it's the case in the D6 but you could try replacing them.  Since the battery input is not protected it's possible/likely that over its lifetime someone accidently touched the battery to the connector terminals backwards, if only for a moment...  Just an educated guess on my part.  Can't hurt.

Roadie, replace all the caps for better sound.  16v was probly too much, but also did you check your polarity before you plugged it in?  The outer shield of the plug should be the +9v, the inner tunnel is ground.  I don't know details about the BC238 resisting reverse polarity, but it's possible that a reverse polarity will fry it, particularly at that voltage.  So check if your 16v plug had correct polarity.  If it didn't, definitely replace the 100 uF cap and the tantalum after this as well! 

 

[craptical]

Yes, I will try that then. Thanks! Actually it reminds me, my E7 went down the same route as once a roadie's; lent it to a friend who fed it with AC (@ 9V only) and BOOM, BC238 smoked. This was over 10 years ago and it didn't occur to me to replace more than the transistor, but better late than never, I will now replace the zener and resistor too (and the transistors), though it does work normally as far as I can tell (except for the noise...). I report back as soon as I have the time to look into it!

Best,

/Dave

 

[once a roadie]

Hey - thanks...I'm not sure of the polarity...I plugged in a 16 V AC unit for a seymour duncan twin tube pedal...not sure if the barrel is (-) or not...not clearly marked...

here are a few words from the manual:

3 Power Jack – This is where you connect the provided wall-mounted power supply
(“wall wart”) to the Twin Tube Classic. Note: it is a 16 VAC/600mA unit. Do not try
to substitute a DC power supply or another AC supply with a different
voltage value or current rating. If you lose your transformer or if it breaks,
contact an authorized Seymour Duncan dealer for a replacement. As an alternative,
for North America and Japan, you can order a 16 VAC/600mA transformer from
Digi-Key (www.digikey.com). The part numbers for each common voltage are as
follows:
1. North America: 120 Volt/60Hz – Digi-Key part # MT7123-ND

 

[craptical]

There are no polarity markings on an AC unit as current is alternating all the time. So, it's the wrong polarity half the time and it will eat the BC238 any way you connect it! Use DC only!

Best,

/Dave

 

[once a roadie]

duh.  thanks

 

[once a roadie]

hey - in the E7 that I connected 16 VAC to...

i replaced the bc238, 8.2zener and 100uF filter cap...

it works but I get a strong harmonic whine max amplitude centered around 1.3kHz, it is also there at multiples (2.6k, 650 Hz, etc) at a lesser degree...

what is it - something unstable?

 

[tommypiper]

hey - in the E7 that I connected 16 VAC to...

i replaced the bc238, 8.2zener and 100uF filter cap...

it works but I get a strong harmonic whine max amplitude centered around 1.3kHz, it is also there at multiples (2.6k, 650 Hz, etc) at a lesser degree...

what is it - something unstable?

No idea.  But for starters you may need to replace the other transistors....  I would also replace the tant...  Does it go away when the filters are switched out?  If not, then you know it's not in the EQ filters.  There are not many other parts...

 

[once a roadie]

OK - I was also thinking the transistors might be the next thing to try...

So, where is the best place to get the transistors and what type should I use?

thanks so much

hey - in the E7 that I connected 16 VAC to...

i replaced the bc238, 8.2zener and 100uF filter cap...

it works but I get a strong harmonic whine max amplitude centered around 1.3kHz, it is also there at multiples (2.6k, 650 Hz, etc) at a lesser degree...

what is it - something unstable?

No idea.  But for starters you may need to replace the other transistors....  I would also replace the tant...  Does it go away when the filters are switched out?  If not, then you know it's not in the EQ filters.  There are not many other parts...

 

[Whoops]

Hello,
I'm servicing a Clavinet E7 at the moment.

I would like to ask you opinions on the Hiss mods described in this video from Vintagevibe:

https://www.youtube.com/watch?v=47ZnyzLW2Hk

It recommends soldering 2 extra capacitors.
One 100pf between Base and collector of the input transistor and one 470pf between base and collector of the output transistor.

Here is a schematic with the mods in red:

It removes the Hiss and some people like it, but there's also opinions that it kills the tone of the clavinet since it forms a Low Pass Filter.

What are your opinions on this?

Thank you so much

 

[Bo Deadly]

That's just going to reduce gain. It's hard to say how much it would reduce the gain because the grounded emitter makes it difficult to predict. Adding the cap does not low pass but because the gain is reduced the RC of the 10n and grounded emitter is going to shift the high-pass RC down a little so it will be a little more bassey. But since the whole circuit is a constillation of high-pass filters, I'm not sure that is the best course.

I have to wonder if they thought the cap would cause a high-cut effect. It will not but the rationale might be correct. A high-cut might help with hiss (since the whole thing is high-pass and more high-passing the hiss must be all high freq). In particular you could try putting the 470p from the output side of the 30K to ground. If the cap is bigger it will start to reduce gain as well.

Also, replace the 100u filter while you're at it. That might help a little with noise.