New (to me) HiFi Studio 1M Bug Bash

[0x29a]

Hey boomboxery! First post! Glad to be here!

I'm looking for some input from fellow owners / techs that know the HiFi Studio 1M fairly well. I'm located in NYC and just had a great condition S1M delivered all the way from Deutschland. It arrives well wrapped, protected for transport (and quarantine screening), and the box itself looks immaculate. Turning it on is a different story... a familiar story. Sound off on the below if you've got a hunch!



She's shiny!!

• In order to get the box to run on US mains (110), I replaced the single middle slot fuse with one 1A fuse each in the left and right slots. I've seen that in the tech manual and elsewhere online. Unfortunately, hitting the main on/off I get a momentary quiet hum in the monitors but it quickly fades away to nothing. No other functions work. The prior owner showed videos (dated when I purchased) of it working happily on European mains (220). Trying to debug this one, thinking maybe one of the caps is bad? Or if someone is familiar with the transformer layout here, maybe one of the transformers is shot? See TR1, and what I'm guessing is TR2 below. Or maybe there's something else I'm not doing, a switch to flip somewhere??
  
  
  
  
• Moving along from that, I'm thankful to discover that the box turns on when using an external 12v power supply. Tested through radio function, aux inputs, all work. And the speakers sound great, just a bit weak when cranked. I've read that these things thump when on mains power, but don't get enough juice otherwise. Is this the case? Also, the facade illumination worked in the video he sent me, but none of the lights come on now. Is this also because the box is running off 12v?
  
  
• In the video he sent, the cassette player was working just fine. Currently however, when I press the play button it doesn't click into place. The tape starts rolling, VU meters jump a little bit, but the button won't stay down. Nothing sounds broken, all other tape functionality works fine (ff/rw, stop, pause). I haven't tried to record. Is there something about these tape decks that are finicky?

Let me know if any of these issues sound familiar to you. I know it's not the gentlest trip over for these heavy things, so I wouldn't be surprised if something jostled lose. At any rate, just trying to get a head start on where to begin tinkering, and maybe what to leave alone.

Again, glad to be here. Thanks for the time!!

 

[Reli]

These models sound like junk with batteries, so I would imagine they sound like junk on the 12V input as well. The only way to get the full 2x30 watts is with AC power.

 

[Radio raheem]

someone made a battery pack that enabled full power on these years ago, unfortunately i have no info on that...you could also step up to a 15v dc power supply i think that would solve the issue..... you would need to check with someone first as i am no tech though

 

[dubout]

The illumination only works from AC. But there must be a switch to turn it on momentarily when running from batteries if I remember right. That being said the bulbs are being know to be busted and mostly don't work.

 

[JimmieJam]

Im an electrician ..the diagram doesnt look like what i'm used to seeing . If I could see the cord end and a european outlet I could figure it out . Or Id install a 220 outlet just for it as an option.

 

[Valde]

Wow, this is an very nice unit. I'm not surprised that the sound is disappointing. On battery power the rail supply to the output stage is only 11.4VDC, on mains supply the rail voltage is 51.1VDC!! This is overkill compared to any other boombox and the difference in power would be about 5W on battery and up to 60W from mains voltage. Over to your problem, I don't own an HiFi Studio 1M but I will try to give you some advice. I don't know if you have an multimeter, if not, try to borrow or by one.
1) Put the fuse back in the original position (B =220VAC) and remove fuses from positions (A). Measure the resistance at the end of the power cord whit the cord connected to the unit. With the power switch in on position, the meter should read >100Ω. If not, check that the power cord is ok, that the plug gives good contact in the unit, the fuse have good contact in the holder and that the switch (S1) is ok.
If measurement is ok >100Ω, remove fuse (B) and install both fuses (A). now the resistance should be reading half ~50Ω. If not, clean the fuse holders, check the fuses with the multimeter ~0Ω.
2) If step 1 is ok. Put fuses in (A) position, plug in the wall plug and measure the "control voltage". Set the meter to DC and measure between "M506" and "M507", should be about 21VDC.
3) Measure the transformer secondary for the output stage. Set the meter to AC and measure between "M505" and "M504", should be about 36.5VAC.

Just post your results, and good luck with the troubleshooting.

 

[GustavoBM]

Wow, this is an very nice unit. I'm not surprised that the sound is disappointing. On battery power the rail supply to the output stage is only 11.4VDC, on mains supply the rail voltage is 51.1VDC!! This is overkill compared to any other boombox and the difference in power would be about 5W on battery and up to 60W from mains voltage. Over to your problem, I don't own an HiFi Studio 1M but I will try to give you some advice. I don't know if you have an multimeter, if not, try to borrow or by one.
1) Put the fuse back in the original position (B =220VAC) and remove fuses from positions (A). Measure the resistance at the end of the power cord whit the cord connected to the unit. With the power switch in on position, the meter should read >100Ω. If not, check that the power cord is ok, that the plug gives good contact in the unit, the fuse have good contact in the holder and that the switch (S1) is ok.
If measurement is ok >100Ω, remove fuse (B) and install both fuses (A). now the resistance should be reading half ~50Ω. If not, clean the fuse holders, check the fuses with the multimeter ~0Ω.
2) If step 1 is ok. Put fuses in (A) position, plug in the wall plug and measure the "control voltage". Set the meter to DC and measure between "M506" and "M507", should be about 21VDC.
3) Measure the transformer secondary for the output stage. Set the meter to AC and measure between "M505" and "M504", should be about 36.5VAC.

Just post your results, and good luck with the troubleshooting.
View attachment 51996

Hi! I'm in the process to restore my Studio 1 and measuring the values you specified I obtained 42 VAC and 23 VDC. Are those values harmfull to the system or not? If not, how to get them on track? Thanks in advance!