Upgrade TA7136P1 in Phono and Tone board

[EchoWars]

If they are an improvement, can one of you Brainiacs D) make a post on how to do it for the SX-780 or other units?

The 780 powers the 7136 devices with +21/-19V. There's a short list of opamps that will work with such high voltages (the OPA604 and LME49870 are two that spring to mind).

 

[samc777]

Will these be for simple replacement of a failed TA7136 chip, or do they actually improve the units they fit in?

Speaking of that, what other Pioneers use the TA7136 chip?

If they are an improvement, can one of you Brainiacs D) make a post on how to do it for the SX-780 or other units? :yes:

elvi,
I've added this post as a recap list for the SA-6800 in my Pioneer Recap list thread! :thmbsp:

The original chip installed in the Pioneer SX-780 was a TA7136P1. Little Diode in the UK claims to have a couple. Our favorite auction also has a few Far East sellers claiming Stock on hand.

Parts.pioneerelectronics.com is out of stock on the original TA7136P1 but does list two alternates, a TA7136AP and TA7136P. The AP chip is NIS but the TA7136P shows as on hand and available for sale at $14.75 each.

So, for those wishing a chip replacement as the quick fix then dust the cobwebs off your wallet and buy the approved sub.

For those wishing to try a new Texas Instruments OpAmp OPA series then the BrownDog adapters from Cimarron Tech seems a good option. I've got both choices on order and will post a "How to" with pictures if the adapters work out. Will they be an improvement? We will find out.

As I researched my options I discovered that the TA7136 chip is used in a number of Japanese stereo boxes. A google search brought up numerous installations.

So at this point I'm awaiting goodies in my mailbox and will move forward when the parts arrive.

I discovered today that after removing the failed Right side chip the Left side Amp now works perfectly and plays music. That to me confirms that the Right side chip has indeed "failed". That negates the need for a chip test that I was looking for previously.

Dave

 

[markthefixer]

The 780 powers the 7136 devices with +21/-19V. There's a short list of opamps that will work with such high voltages (the OPA604 and LME49870 are two that spring to mind).

Shame on me, I neglected to address the voltage levels at the power pins for the ta7136 type chips...

the ta7136 draws 3 to 4 mA per chip, so some zener and resistor regulators could be added to open up the possibilities.

The individual models must be evaluated for any op-amp power supply mods, the:

sx-550 (2; phono) both these voltages are developed by voltage dividers, the addition of 15v zeners (could be ON the adapter) will both pull the voltage down, and regulate the voltage at a max of 1/4 watt dissipation.

sx-650 (2; tone) these will need some on-adapter-board 510 ohm 1/4 watt resistors in addition to the 15v zeners, since the discrete phono amps also need the +21v and -19v

sx-750 (4; phono & tone) this one looks easy, replace D12 and D13 in the unit with 15v zener diodes, they are exclusive to the op-amp's power

sx-780 (2; tone) add a 15v zener across c303 and another 15v zener across c304 in the unit.
sx-880 (2; tone) add a 15v zener across c215 and another 15v zener across c216 in the unit.


512-1N5245B Fairchild 15 V, 0.5W Zener

there are also 8 pin dip DIY adapters on eBay, out of Boise, Idaho
hint: on all searches drop the "ap" to search for ta7136 as well as ta7136ap...

 

[samc777]

Shame on me, I neglected to address the voltage levels at the power pins for the ta7136 type chips...

the ta7136 draws 3 to 4 mA per chip, so some zener and resistor regulators could be added to open up the possibilities.

The individual models must be evaluated for any op-amp power supply mods, the:
sx-780 (2; tone) add a 15v zener across c303 and another 15v zener across c304 in the unit.

512-1N5245B Fairchild 15 V, 0.5W Zener

there are also 8 pin dip DIY adapters on eBay, out of Boise, Idaho
hint: on all searches drop the "ap" to search for ta7136 as well as ta7136ap...

The "4 sold" on the Boise Link are headed this way. I found those before the BrownDog units. May as well try all combinations.

The BrownDog adapters have the advantage of using either the pin or surface mount chips while the Boise adapters accept pin chip only.

Thanks for the info on the Zener additions, I have 13V, 14V and 16V on hand but not 15V. I will add the 15V zeners to my next mouser order.

I assume that the use of either the 14V or 16V zener in place of the 15V should be ok as the data sheet shows an approx +/- 1.5V range for all 3 zeners?

This should be an interesting experiment.

Dave

 

[markthefixer]

choice between 14 and 16 means go with 14, safer...

 

[mgrisoli]

Shame on me, I neglected to address the voltage levels at the power pins for the ta7136 type chips...

the ta7136 draws 3 to 4 mA per chip, so some zener and resistor regulators could be added to open up the possibilities.

The individual models must be evaluated for any op-amp power supply mods, the:

sx-550 (2; phono) both these voltages are developed by voltage dividers, the addition of 15v zeners (could be ON the adapter) will both pull the voltage down, and regulate the voltage at a max of 1/4 watt dissipation.

sx-650 (2; tone) these will need some on-adapter-board 510 ohm 1/4 watt resistors in addition to the 15v zeners, since the discrete phono amps also need the +21v and -19v

sx-750 (4; phono & tone) this one looks easy, replace D12 and D13 in the unit with 15v zener diodes, they are exclusive to the op-amp's power

sx-780 (2; tone) add a 15v zener across c303 and another 15v zener across c304 in the unit.
sx-880 (2; tone) add a 15v zener across c215 and another 15v zener across c216 in the unit.


512-1N5245B Fairchild 15 V, 0.5W Zener

there are also 8 pin dip DIY adapters on eBay, out of Boise, Idaho
hint: on all searches drop the "ap" to search for ta7136 as well as ta7136ap...

Hi Mark,

I know this thread is very old, however I have a bad TA7136P1 in the tone control of my SX750 and I was reading it through to implement install a browndog adapter with a POA604 as an alternative.
When you say "replace D12 and D13 in the unit with 15v zener diodes" - what exactly you mean?
I can't find a reference to D12 D13 on any of the boards and schematics.
There are a couple zeners in the power supply assembly (AWR099) marked as D11 and D12, but the tone control board pulls DC (21V and -19V) from the power amp pins #21 and #28 respectively, there are couple diodes around 28 but no zeners.

Can you help me with some guidance?

M

 

[satellite65]

D12 and D13 are on the main board, inboard from the tape jacks, next to pins 35 and 36.

 

[mgrisoli]

D12 and D13 are on the main board, inboard from the tape jacks, next to pins 35 and 36.

Heck, right on my face!

Can you tell if this conversion has to happen on the tone control board an also phono stage? (I am assuming changing these zeners would impact both...)

Thank you for the assistance.

M

 

[satellite65]

Now that you mention it, there is a line from -19V on the Phono Amp feeding the FM filter and muting circuit.
I'm not sure if the change from -19V to -15V would be detrimental to these FM circuits...
You could separate that and run FM off of an added dropping resistor and 19v Zener off of the -37v supply from the power amp.

If you went ahead with 15V Zeners for D12 and D13, I would increase wattage on R1 and R2 on the power amp.
These drop +33V and -37V from the amp board to the D12, D13 Zener voltages.
They are rated at 1W. The negative side especially would be very close to 1W actual dissipation with a 15V Zener for D12.

 

[markthefixer]

Two things to remember;
THIS was a SA-6800
YOU are addressing a SX-750.
Be careful on those bootlegger 180 degree turns....

Satellite's post came in as I was checking both. He's on the right track.

 

[mgrisoli]

Two things to remember;
THIS was a SA-6800
YOU are addressing a SX-750.
Be careful on those bootlegger 180 degree turns....

Satellite's post came in as I was checking both. He's on the right track.

Oh, I was referring to a sentence that you posted:

sx-750 (4; phono & tone) this one looks easy, replace D12 and D13 in the unit with 15v zener diodes, they are exclusive to the op-amp's power

I know this thread is about an SX-6800, but that it is not a complete 180 degree turn if you mentioned the same approach could be used on a 750, right?

Perhaps to update the zeners D12 and D13 and the resistors R1 and R2 may not be sufficient... given the FM Filtering and Muting circuit @satellite65 mentioned:

Now that you mention it, there is a line from -19V on the Phono Amp feeding the FM filter and muting circuit.
I'm not sure if the change from -19V to -15V would be detrimental to these FM circuits...

Do you have a suggestion on what else could do to avoid the problem?

M

 

[Watthour]

Possibilities may be the LF356N series or LM741 series OP-amps.

 

[elvi]

(BTW, thanks to the experts here, the SA-6800 project worked wonderfully. I'm listening to it now. (My HK 800+ failed, and I pulled it out, and placed it on the restore next pile))

 

[markthefixer]

Just spitballing here, would have to calculate actual values.

Adapter board has a ground? run the power over to the adapter board with resistors, and have zener diodes on each adapter board just for that adapted component. Could add caps across the zeners to be sure the power is clean.

 

[zebulon1]

I'd like to insert this post for added discussion info:
I have a Technics SA-1000 that uses the TA7136 op-amps. There is six of them. Using these BrownDog adapters and OPA604's made a wonderful difference.

The thread is found here

 

[markthefixer]

nice...

OPA604 has a +/- 24v power supply range. Granted mouser wants about 3 bucks apiece, but who wants to cheap out at that point?

 

[zebulon1]

That’s what makes this particular device work in that preamp. The Technics runs +-20 volt rails. Not many low distortion op-amps have those spec’s.
Rcs16 suggested the decoupling caps. I’m not that smart.
The adapters were over $35 for the six.
$20 for the amps.
It adds up.
It reminds me of this problematic vintage Snap-on tool box I restored. At some frustration point, I didn’t care if cost a million dollars, it was going to get done.

 

[mgrisoli]

That’s what makes this particular device work in that preamp. The Technics runs +-20 volt rails. Not many low distortion op-amps have those spec’s.
Rcs16 suggested the decoupling caps. I’m not that smart.
The adapters were over $35 for the six.
$20 for the amps.
It adds up.
It reminds me of this problematic vintage Snap-on tool box I restored. At some frustration point, I didn’t care if cost a million dollars, it was going to get done.

I see that you removed one resistor and one capacitor for each TA7136 you replaced. Can you elaborate on that?
To which pins of the TA... they were connected to and why you remove them?
Also, couldn't you have soldered that decoupling cap on the main board?
Sorry I am not looking at the schematics of your receiver, I am just looking at the pictures...

M

 

[zebulon1]

No and no.
You have to isolate the disconnected circuit. Mr Relish explains that better than I could. The components are not needed in the circuit. Looking at the op-amp data sheets shows the installed circuit and is self explanatory.
The decoupling caps are to prevent the oscillation of the susceptible op-amps.

 

[rcs16]

The adapters were over $35 for the six.
$20 for the amps.
It adds up

One day I'll make an adapter for the TA7136, something like this one I did up recently for another product.
There can be a few tricks to using a regular +/- 15 to 18V opamp, like putting a couple of zener diodes in series to drop the voltage down. Any other ideas?

Imo, there is really nothing wrong with the TA7136. I have a customer who has a Marantz 2385, it uses the TA7136 in the pre-amp. He says the 2385 sounds better stock than the serviced Pioneer SX-1980 that he has. One persons opinion, not necessarily mine.

Rick