JVC VR-5525 (LX) schematics

[Bert Beukema]

Hi guys,

I'm working on a nice JVC VR-5525 receiver. It had several issues but they were all resolved. One issue remains: crackling on the right channel. I believe I have traced this problem to a single 33uF cap in the pre-amp. It is difficult to trace further because of the way it is constructed.

Problem is: to get at the PCB requires a serious amount of deconstruction of the machine. It is nearly impossible to reach it and it is fixed with at least 30 wires. Also the tuner thread is running through the pcb area and the case. To get it out will take me at least two hours of fumbling, cursing and then I need to rewire the entire shebang (it's all wire wrapped).

So I need to have a bit more security in the analysis but I can't find a schematic or service manual of this machine anywhere. The 5515 is roughly the same power amplifier, but a much different pre-amp. The 5535 is totally different.

Does anyone have acces to either a schematic or a service manual?

Kind regards,

Bert

 

[Bert Beukema]

Hmmm. Close by to that capacitor is something designated IC542 labeled as FA6012. This an odd thing. It appears to be a blob of some kind, not a regular IC at all.
The JVC VR-5535 also has them. This crackling sound is something I would normally associate with a failing transistor.
Could it be that the IC is failing? I have no idea if that IC is somehow reverse engineerable; although it doesn't seem very complicated.

 

[Bert Beukema]

Hmmm. 5535 service manual shows me the IC equivalent. I've seen this before.
Easy to rebuild. But still, before doing such extensive work the question still stands.

 

[Jed98]

Hmmm. Close by to that capacitor is something designated IC542 labeled as FA6012. This an odd thing. It appears to be a blob of some kind, not a regular IC at all.
The JVC VR-5535 also has them. This crackling sound is something I would normally associate with a failing transistor.
Could it be that the IC is failing? I have no idea if that IC is somehow reverse engineerable; although it doesn't seem very complicated.

Hi, I have a JVC VR-5525 and my audio tech guy has informed me that that the FA6012 is causing the problem and there don't appear to be any spares around. Does anyone know a way around this problem? Is there anyone around that has obsolete parts or is there something else that it could be replaced with.
Regards
Jed98

 

[Bert Beukema]

Hi, I have a JVC VR-5525 and my audio tech guy has informed me that that the FA6012 is causing the problem and there don't appear to be any spares around. Does anyone know a way around this problem? Is there anyone around that has obsolete parts or is there something else that it could be replaced with.

I have posted the equivalent circuit above. Your tech can quite easily build it, it is very simple. Just build the little IC and replace the broken one.
It is just that in my vr-5525 to replace the IC is a lot of work and requires dismantling the front of the receiver as well as removing the dial string for the tuner.
That is time consuming and a pain to do, much more work than building the IC itself.

 

[Glenz75]

Hi, thanks for this 'fix' for these JVC's and other models that use the FA6012. I built one up on veroboard, installed it and problem solved both channels are now balanced and noise free on this VR-5525. Just a note on the drawn circuit diagram there is a 47k resistor off the emitter of the first transistor and another 47k to the collector of the second transistor, these are both meant to be 4.7k so make those values are used, and then you won't find out the hard way like I did!

 

[Bert Beukema]

Hi, thanks for this 'fix' for these JVC's and other models that use the FA6012. I built one up on veroboard, installed it and problem solved both channels are now balanced and noise free on this VR-5525. Just a note on the drawn circuit diagram there is a 47k resistor off the emitter of the first transistor and another 47k to the collector of the second transistor, these are both meant to be 4.7k so make those values are used, and then you won't find out the hard way like I did!

Super work!
Exactly as I was suspecting, that IC is prone to failure. Good to know that we can now confirm the cause of the issues in these machines.
I have made two already but did not find the time to dismantle my JVC.
I did use 4.7k resistors because 47k seemed way too high but again, very nice for confirmation.

 

[Manu54]

Salut,
je dois réparer un ampli jack vr-5525 qui produit du souffle sur les 2 voies. Je soupçonne depuis un bon moment les circuits FA6012 et vous confirmez mes soupçons. Merci pour le schéma équivalent pour remplacer le circuit . Je voudrais simplement savoir quelle est la référence des transistors utilisés svp. Merci beaucoup pour votre retour.

 

[Bert Beukema]

Salut,
I have to repair a vr-5525 jack amp that produces noise on both channels. I have suspected the FA6012 circuits for quite a while and you confirm my suspicions. Thank you for the equivalent diagram to replace the circuit. I would simply like to know what is the reference of the transistors used please. Thank you very much for your feedback.

There are 2SC458 transistors in the pre-amp, these will most certainly generate hiss. You can change them for 2SC1845 or 2SC2240.
When rebuilding the IC you can use these transistors as well. 2SC1815 would also work. Many transistors would work, it is just a bog standard small signal transistor.

BB

 

[Manu54]

Bonsoir,
Merci beaucoup pour toutes ces informations. J'ai déjà remplacé les transistors sc458 par des 2sc2240. Il m’en reste , je peux les utiliser pour fabriquer les modules de remplacement de FA6012 ? Merci pour votre réponse.

 

[Bert Beukema]

Yes. You can use C2240 to build the FA6012 IC.

 

[Manu54]

Bonjour,
Merci encore pour vos réponses. Désolé de ne répondre que maintenant. J'ai eu beaucoup de travail. Je vais réaliser les 2 montages pour remplacer mes FA6012. Juste une question, sur le schéma donné, je vais remplacer les 2 résistances de 47K par 4,7K mais il y a aussi une résistance de 57k si je lis bien ? Sur le collecteur du premier transistor. Est-ce la vraie valeur ? Ce n'est pas dans la série E12. Est-ce que 56k est correct ? Merci.

 

[Bert Beukema]

Bonjour,
Merci encore pour vos réponses. Désolé de ne répondre que maintenant. J'ai eu beaucoup de travail. Je vais réaliser les 2 montages pour remplacer mes FA6012. Juste une question, sur le schéma donné, je vais remplacer les 2 résistances de 47K par 4,7K mais il y a aussi une résistance de 57k si je lis bien ? Sur le collecteur du premier transistor. Est-ce la vraie valeur ? Ce n'est pas dans la série E12. Est-ce que 56k est correct ? Merci.

If you use a 56K resistor it will work just fine, no problem.
These "IC's" are not very tight in their electronics. Anything within 10% will do fine.

BB

 

[Manu54]

Ok, thank you very much. I'll give you some news when it will be done.

 

[Bert Beukema]

Good luck!

BB

 

[Manu54]

Bonjour,
Je reviens vers vous pour valider le schéma proposé pour remplacer le circuit FA6012. J'ai redessiné et monté avec les points de connexion et les valeurs des composants pour être sûr. veuillez me confirmer que c'est correct svp. Merci beaucoup.

 

[Bert Beukema]

Brilliant Manu! Thanks for the updated schema, this will surely help others!

BB

 

[Jag33]

Bonjour, merci pour ce schéma car je recherche un FA6012 et vais peut être le traiteravec composants sur veroboard. Cependant je note une laison incorrecte: la broche 2 relie la base du premier transistor à son émetteur, ce qui a pour effet de le bloquer. Je ne suis pas non plus certain que la patte 5 soit reliée à l'émetteur du 2eme transistor.
Avez vous déja corriger des choses sur ce schéma?