Car Radio Tape as AUX input

Thread Starter

Fazen

Joined May 20, 2020
8
So i removed the mechanism and replaced tape audio with AUX lines with no result (via
pins (L3, R3) of the volume controller IC151) so I figured out that the system controller
(IC501) is testing for some conditions to send tape audio for processing :
the tape must be loaded and the supply/takeup reel must be spinning, because empty tape
(with no magnetic tape inside) gets ejected. The solution is to insert a blank tape to listen to
AUX input.
The problem is that the tape mechanism is taking up space needed for a power supply
module and it has to go away.
So I measured the voltages at the mehanism connector (CN352) when tuner is on (tape
off) and when the tape is playing: (H = 4.7v, L = 0v)

Pin Description Tuner Mode Tape Mode
---- ---------------- ------------ ------------
1 * C-MOTOR L Vcc <<<
2 GND L L
3 LM+ L L
4 LM- L L
5 * POS2 H L <<<
6 * POS1 L H <<<
7 POS3 H H
8 GND L L
9 * POS4 L H <<<
10 AUTO. MTL L L
11 * REEL1 H [L ~ 3.3v] <<<
(Alternating)
12 REEL2 (N/C)
13 * B+ (8.5V) L B+ <<<

So I concluded that pins (1, 5, 6, 9) must be set accordingly, and I guess that pin 11 is the

reel rotary encoder stroboscopic signal or something, and I have no idea how to simmulate

that. If someone can help me bypass the mechanism and make the system controller

believe a tape is there and playing, that woud be great.

Thank you very much for any help or suggestion.
 

Thread Starter

Fazen

Joined May 20, 2020
8
Hi. i have a CX R5080R car radio player tha t i want to use its tape mode as AUX input.
So i removed the mechanism and replaced tape audio with AUX lines with no result (via
pins (L3, R3) of the volume controller IC151) so I figured out that the system controller
(IC501) is testing for some conditions to send tape audio for processing :
the tape must be loaded and the supply/takeup reel must be spinning, because empty tape
(with no magnetic tape inside) gets ejected. The solution is to insert a blank tape to listen to
AUX input. The problem is that the tape mechanism is taking up space needed for a power supply
module and it has to go away. I measured the voltages at the mechanism connector (CN352) when tuner is on (tape
off) and when the tape is playing: (B+=12v, H = 4.7v, L = 0v)

Pin Description Tuner Mode Tape Mode
---- ---------------- ------------ ------------
1 * C-MOTOR L Vcc <<<
2 GND L L
3 LM+ L L
4 LM- L L
5 * POS2 H L <<<
6 * POS1 L H <<<
7 POS3 H H
8 GND L L
9 * POS4 L H <<<
10 AUTO. MTL L L
11 * REEL1 H [L ~ 3.3v] <<<
(Alternating)
12 REEL2 (N/C)
13 * B+ (8.5V) L B+ <<<

So I concluded that pins (1, 5, 6, 9) must be set accordingly, and I guess that pin 11 is the
reel rotary encoder stroboscopic signal or something, and I have no idea how to simmulate
that. If someone can help me bypass the mechanism and make the system controller
believe a tape is there and playing, that woud be great.
Thank you very much for any help or suggestion.
 

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Externet

Joined Nov 29, 2005
1,493
Seems a case as in my vehicle stereo.
The key is to identify which IC does the audio management; -use data sheets or schematic if available- and lift the 'tape' corresponding pins from their traces and enter the auxiliar L,R into those pins with capacitors if there is DC bias present.
Depending on the model/brand, you may need to fake presence of cassette-in to its sensing switch. Sometimes one of those audio injecting cassettes with no tape becomes necessary to keep in the player just to engage the auxiliar select by choosing 'tape'

That is the way I had to go. An audio head injecter cassette with cables cut off; real L,R auxiliar added jack lines to the lifted pins of the audio management chip, the one that routes the AM, CD, tape, FM1, FM2, VHF, audio to the volume manager and power amplifier input.

The volume control is not a convenient auxiliar entry point any more since digital 'potentiometers' are implemented in newer units. Another way is a stereo cancelling jack on the front panel, hooked to any FM or the power amplifier input traces.

If you are in need of space for a supply instead of the tape mechanism, ?¿? you are not using thew unit in a vehicle ? Do you have a schematic ?

Edited : added ----> Saw the schematic in another thread; seems to me that you can feed AUX into CNJ150 bus by schematic coordinates B22. No modifications; unit is prepared for AUX waiting for your wishes come true.
 
Last edited:

schmitt trigger

Joined Jul 12, 2010
242
The Tape preamp circuitry will have, in addition to lots of gain not suitable for line level signals, a significant de-emphasis. If my memory serves me correctly, it is 75 uSec de-emphasis.
This means in addition to clipping, your treble frequencies will be muted.

And we haven't touched Dolby EQ yet.

My suggestion? *Bypass all that circuitry completely.*

How to do it? Lift the negative terminals of C308 and C408, and attach your stereo signals there. And ground of course.


BTW, what brand is it? Is it a Sony?
 

Thread Starter

Fazen

Joined May 20, 2020
8
Hi,
that's what i did, but no sound is ouput unless a tape is loaded and playing !!!
the unit is a Sony XR C5080R. I joined a link for the service manual with diagram and everything.
Thanks
 

Externet

Joined Nov 29, 2005
1,493
OK, I did not know that bus feature without an user manual.
Check pins 5 and 26 for IC 351. Would need audio fed to lifted from gnd C309 and C409. And look for the enabling path, perhaps pin 18 high - or pin 17 ?? Look at is data sheet.
 
Last edited:

Thread Starter

Fazen

Joined May 20, 2020
8
according to CXA2509AQ datasheet (IC351), it's a Two-system (TAPE/AUX) input select switch, and pins 17, 18 are INPUT pins. so I guess the sys. control. IC501 is the one making selection based on the Loading mechanism state, and Reel1 signal to send a LOW into pin17 of IC351, which is always the case (on the diagram). so IC351 is processing only signals from tape input (4, 27).
 

Thread Starter

Fazen

Joined May 20, 2020
8
You are confirming what i had in mind, Dodgydave !!!
I just have to decide whether to buy an oscilloscope, or tear down the mechanism for the rotary encoder under the take-up reel (I guess) to determine the characteristics of the square wave in question. I'll keep you informed anyway. Thanks alot guys !!!
 

Externet

Joined Nov 29, 2005
1,493
...and pins 17, 18 are INPUT pins...
Cannot be, inputs to that chip are pins 4,27 (normal tape) or 5,26 (the aux. you want). Pins 17, 18 can/should be input select ! Make sure.

This gadget avoids the need to tamper with the tape motion sensor :
----> https://www.wish.com/product/5a85204d1c6def6c49fd51bf?hide_login_modal=true&from_ad=goog_shopping&_display_country_code=US&_force_currency_code=USD&pid=googleadwords_int&c={campaignId}&ad_cid=5a85204d1c6def6c49fd51bf&ad_cc=US&ad_lang=EN&ad_curr=USD&ad_price=1.93&campaign_id=7203534630&gclid=EAIaIQobChMI0f2woezC6QIVTtbACh2UQQggEAQYAiABEgKAJvD_BwE&share=web

Cut off the cable as the audio is horrible that way, that is why should be fed to the proper lifted pins.
 

Thread Starter

Fazen

Joined May 20, 2020
8
Cannot be, inputs to that chip are pins 4,27 (normal tape) or 5,26 (the aux. you want). Pins 17, 18 can/should be input select ! Make sure.

This gadget avoids the need to tamper with the tape motion sensor :
----> https://www.wish.com/product/5a85204d1c6def6c49fd51bf?hide_login_modal=true&from_ad=goog_shopping&_display_country_code=US&_force_currency_code=USD&pid=googleadwords_int&c={campaignId}&ad_cid=5a85204d1c6def6c49fd51bf&ad_cc=US&ad_lang=EN&ad_curr=USD&ad_price=1.93&campaign_id=7203534630&gclid=EAIaIQobChMI0f2woezC6QIVTtbACh2UQQggEAQYAiABEgKAJvD_BwE&share=web

Cut off the cable as the audio is horrible that way, that is why should be fed to the proper lifted pins.
here's the datasheet, look on page 5 !
https://www.alldatasheet.com/datasheet-pdf/pdf/46783/SONY/CXA2509AQ.html
 

Externet

Joined Nov 29, 2005
1,493
"here's the datasheet, look on page 5 ! "

----> That page 5 clearly tells pin 17 to be input select switch INSW


Pin 17 also shows as input select on page 17 of the data sheet !
Pull pin 17 high to use pins 5,26 as the auxiliar input you want, you should be able to get your AUX without removing the tape deck.
Page 13 shows how the chip does it .
 
Last edited:

Thread Starter

Fazen

Joined May 20, 2020
8
That works great !
sorry for not getting your point from the beginning, i was sticking on the idea of simulating the Reel thing to trick IC501, instead of using the AUX input feature if IC351.
Thank you very much !!!
 
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