HITACHI TRK-W1 buzzing on tape 2

[Funkateer38]

Hello everyone,
I need your help for a HITACHI TRK-W1.
Never opened for 40 years, I have an unresolved problem, a hum only on the FUNCTION of Tape 2 (lower player) with saturation of the equalizer. I cleaned the tape 2's pcb, the heads and FUNCTION selector. Also demagnetized the heads.
Couldn't find the service manual on the internet, any idea please ?

 

[Superduper]

If it has a record/playback switch, clean it. A good percentage of these issues can be traced to that switch.

 

[Funkateer38]

If it has a record/playback switch, clean it. A good percentage of these issues can be traced to that switch.

Hello Super Duper, thank you for your attention to my request. Since posting, I've tested with the batteries and the buzz goes away. I changed the 2200uF 16V capacitor of the power supply but the hum persists with AC power. I'm afraid the transformer is defective.

 

[Superduper]

Why do you conclude that the transformer is defective? The transformer is nothing but 2 windings of wire, that’s it. Unless you are talking about a mechanical hum due to loose transformer laminations. In this case, although there is a hum, it’s not present in the speakers nor would the volume of the hum change. The 60hz hum that is normally associated with PS hum is due to poor filtering of the PS circuitry which the capacitor does most of. Other things can cause it too. Also, in your post, you state that the hum only occurs on tape 2; is this still true? Because an AC hum would occur always.

 

[floyd]

I totally stupid about this but I do think that power supplies have filter caps on them and those might need too. Like I said I don't know what the hell I'm talking about but I have worked on a lot of car amplifiers.

 

[Funkateer38]

Why do you conclude that the transformer is defective? The transformer is nothing but 2 windings of wire, that’s it. Unless you are talking about a mechanical hum due to loose transformer laminations. In this case, although there is a hum, it’s not present in the speakers nor would the volume of the hum change. The 60hz hum that is normally associated with PS hum is due to poor filtering of the PS circuitry which the capacitor does most of. Other things can cause it too. Also, in your post, you state that the hum only occurs on tape 2; is this still true? Because an AC hum would occur always.

More precisely, in Tape 1 mode, the hum is strong and the level indicator lights up at MAX. in the other Tape 2, RADIO and AUX modes, this buzz is very weak even when thoroughly cleaning the FUNCTION selector and resolderings. Phenomenon which disappears with the use of external batteries. The service manual is not present on the internet and with my limited knowledge, I will test with a 12V electric charger.
Merci à tous pour votre aide.

 

[Superduper]

If it has a record/playback switch, clean it. A good percentage of these issues can be traced to that switch.

I really think you ought to clean the R/P switch which was my first response to you, but you didn't acknowledge having cleaned it yet. There are many suggestions and recommendations here in the archives regarding the best way to clean it. I know because I've spoken about this myself probably dozens of times. YES your boombox has that switch, I can confirm it (see image). It may or may not fix your issue, but it costs nothing to clean and just based on experience, it's the very first switch to clean in any boombox because dirty connections there causes so many problems.

 

[Radio raheem]

I totally stupid about this but I do think that power supplies have filter caps on them and those might need too. Like I said I don't know what the hell I'm talking about but I have worked on a lot of car amplifiers.

There are smoothing caps in these units lad but i wouldn't know where they are located

 

[Funkateer38]

I really think you ought to clean the R/P switch which was my first response to you, but you didn't acknowledge having cleaned it yet. There are many suggestions and recommendations here in the archives regarding the best way to clean it. I know because I've spoken about this myself probably dozens of times. YES your boombox has that switch, I can confirm it (see image). It may or may not fix your issue, but it costs nothing to clean and just based on experience, it's the very first switch to clean in any boombox because dirty connections there causes so many problems.View attachment 55257

Hello, i did it many times in several actions. i see you have you got the service manual. Can you please send me photos about circuit board and schematic diagrams ou share a pdf file on website. Thank you