Technics ST 9038 Op amps modification - diyAudio
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Old 13th August 2005, 06:53 AM   #1
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Default Technics ST 9038 Op amps modification

Howdy everyone..,

According to http;//www.tunerinfo.com my Technics ST 9038 tuner ( 17th untill now ) suffers from 'mediocre' mids due to the 4558 op-amp.
As far as I'm concerned it does'nt sound terribly wrong but any improvement is welcome.
So.., I figured.., change the op-amps for better ones and it might kick the Lux T-117's ***..!

Questions;

- Can a soldering novice like me do this by himself ( I want to modify myself so badly ) or is it better to have it fixed by an soldering hero.

- Witch op-amp would you guy's advise me to use.

- How many op-amps are there ( by estimation ) to change.

Thanks for your replies...,

Robert
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Old 17th August 2005, 01:43 PM   #2
BrianL is offline BrianL  United States
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The Technics should have 2 or 3 in the signal path (they are dual
op-amps). I have a 9030 and it has them in more than one
location. The package is a plastic DIP -- before the days of
surface-mount. The problem these days if finding any op-amps
in DIP packages, but one can always check surplus electronics
stores. I believe the TI/Burr-Brown OPA2134 is still made in a
DIP. Others can be used with an SOIC->DIP adapter board such
as Brown Dog makes.

Choices would include OPA2134, OPA2604, AD8620 and others.
The OPA2134 is probably the less likely to cause problems.

Desoldering and resoldering are easy _IF_ you have reasonable
soldering technique and a solder sucker or solderwick to get
the old part out. I recommend a small diagonal cutters to clip the
leads off the body of the part to be removed and then de-solder
the pins one-by one. That's the safest way.

While you are at it, you could enhance the size of and upgrade
various caps in the signal path -- all the standard tweaks.
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Old 17th August 2005, 01:53 PM   #3
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You will need two, and OPA2134 is indeed a good choice. I tried few others, but those sounded the most natural there. I would also recommend changing coupling caps to BG N 4.7u.
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Old 19th August 2005, 10:26 AM   #4
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OK.., thanks a lot for your replies..!

I've got the idea how to do it and what to use.., it will be the BB OPA2134 DIP.
I asked someone experienced to order them and will try to put them in myself.

Why do you recommend to change the ( coupling ) caps as well?

@ BrianL

You're writing about 'standard' tweaks.., may I humly ask what you to define that?

Robert
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Old 19th August 2005, 02:34 PM   #5
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The tuner will sound better with upgrade coupling caps. The generic electrolytics in a signal path are one of the weak links there.
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Old 21st August 2005, 12:11 AM   #6
BrianL is offline BrianL  United States
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"Standard Audiophile Mods".

Peter mentioned coupling caps.
Also, any electrolytic cap in the power supply or audio section.
(don't mess with RF/IF sections if you don't know what
you're doing)

You might parallel electrolytics with Polypropylene caps.
Replace HiQ ceramics with better ones
One can replace audio section resistors with 1% metal film units.
There are probably voltage regulators in the power
supply and they could be upgraded or replaced with fancy
regulators.

See the FM Tuner Info web site for "Bob's and Jim's Mods".
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