Pioneer m90 issue

[Widzew83rts]

Hi

I have a pioneer m90 , and there is a problem with dispay , display on the left side is lower than right side, sometomes left side disapire. Both chanels plays fine. I checked fuses they are ok

 

[avionic]

Welcome to AK... Might get lucky and just have a bad solder connection on the display board.

 

[avionic]

AWZ-2041 board Circuitry containing IC401,402 and 403.Check solder connections.

 

[Widzew83rts]

Do you think if this is broken thas may be the issue? Please check picture

 

[MattiaM]

That is the lamp indicating that the amplifier is not in protection mode. Even if open, it should have no influence on the meters.

 

[Widzew83rts]

Do you know where can i get this lamp? Unther this lamp it PL 402

 

[MattiaM]

In my recent M90 restoration I used successfully an 8V 170mA axial lamp (20mm in length). You can easily find it online.

 

[Widzew83rts]

Ok thank, do you think the meters are not working corectly becouse i didnt conect the speaker yet? I just plug the amplituner and conect the phone to check if both canals are working

 

[MattiaM]

if the input signal is the exact same for both channels, the meters should display the same signal level. I would not recommend trying that without a load at the speaker terminals. If you are worried there are issues with the amplifier that might ruin your speakers, then use an 8 ohm dummy load with adequate power dissipation (that amplifier can produce 200W per channel into an 8 ohm load, so you will need something very beefy).

With a load attached to the speaker terminals, if you don't have a signal generator, you can use your phone as signal generator; there are on YouTube videos that have frequency sweeps or individual frequencies (e.g. 440 Hz, 1 kHz) at a predefined output, so that you can be sure the signal reaching both channels is the same. With that, if you still observe differences in the L and R power meters, you have an issue somewhere.

 

[Massimogdf]

Good evening. I have had the M90a with me since 2004. Purchased on eBay. It has always worked well. I discovered with other M90a that when you press the power button a red light turns on, after the relay this light turns yellow. This occurs in the center of the front panel. My M90a never had lights, the two small lights in the center of the front panel never worked. The amplifier has always worked well. I recently made an update to the capacitors and transistors for the drivers. I used KSA1381 and KSC3503 to replace A1145 and C2705. All replacement capacitors, even the big 4, with nichicon PW. The M90a sounds better now, but the light still doesn't turn on when I press the power button. I disassembled the front panel, I replaced the two bulbs (one covered with red and one covered with yellow) with other originals. No lights come on yet, but my M90a works perfectly. I ask for your help, you are very good with M90a, if someone has a solution to power these two bulbs. The light as pictured in my M90a does not turn on. Is there a way to power the two bulbs? Thank you all,

 

[Max Martin]

Have same issue but red is working but yellow never comes on...

 

[Massimogdf]

Prova a misurare la tensione ai capi della lampada. Ho risolto il mio problema inserendo due lampadine da 12V. Originariamente le lampade dovevano avere una tensione massima di 8V, ma per qualche motivo sul mio M90a avevo circa 9V a quel punto, questo ha causato la bruciatura di tutte le lampade da 8V che ho acceso. Poi ho deciso di utilizzare lampade a 12V, da circa un anno le due lampade hanno funzionato molto bene. Saluti

 

[Massimogdf]

Try measuring the voltage across the lamp. I solved my problem by putting two 12V bulbs. Originally the lamps were supposed to have a maximum voltage of 8V, but for some reason on my M90a I had about 9V at that point, this caused all the 8V lamps I switched to burn out. Then I decided to use 12V lamps, for about a year the two lamps have worked very well. Greetings

 

[Max Martin]

Ok thx ill try that.
Also tried swapping the sc2705/a1145 to ksc/ksa models as above but no luck. Relays wont click on now.

 

[Massimogdf]

Ho usato TTA004B e TTC004B di Toshiba. Sono pre driver molto veloci e affidabili. Anche KSA1013Y e KSC2383Y sono ottimi pre driver, ma hanno un COB molto alto e questo non va bene. Chiedi, sarò felice di aiutarti.

 

[Massimogdf]

I used Toshiba's TTA004B and TTC004B. They are very fast and reliable pre drivers. KSA1013Y and KSC2383Y are also great pre drivers, but they have a very high COB and that's not good. Ask, I'll be happy to help you.