Porta 07 - damaged electronics (wrong polarity)

[a studio port]

Hi

Someone used the wrong polarity on this PORTA 07, so a few components got damaged inside. I've replaced a few capacitors that looked blown, and a two transistors, including the one screwed to the tape deck.

Now it turns on, but TRACK 1 in TAPE mode gives a loud hum.
In TAPE CUE mode, the mixer seems to be bypassed, all tracks are played a full volume.

Otherwise, everything else seems to work.

There has to be more damaged components i haven't found, but i have no clue how to find them.

Any help ? I couldn't find any schematic.

Thanks

 

[SkywaveTDR]

It all depends on how far down the wrong voltage went as most op amps are quickly destroyed by wrong polarity. The deck will have to be checked channel by channel as to what is blown on it and this might not be cheap to do. It can be fixed as I have fixed them in the past- I used to work for Teac in Chicago. I have some parts on hand- A DVM (Digital Voltmeter) is all you need to test if transistors or Op Amps are bad- If they do not work due to this kind of damage they usually short 1 to 8 if 8 pin DIPs or SIP or the will short to ground if they are fed a bipolar supply. Funny thing is I might be working on one today or tomorrow as one is here.

 

[silki]

Im kinda in the same boat here. So only thing to do is to trash it??

 

[SkywaveTDR]

I never trash unit that are repairable. The only units that I have parted out are those brought to me that were in 11" of water. Those you can not repair unless you want to spend $4000 to do it. Cheaper just to go and buy a better unit that works.

Trashing repairable units is a waste and just causes the price to rise on unit that are remaining around. There were a lot of Porta Studios made and it is strange that such things are still working today. I fix a lot of them.

 

[_esc_]

how did you end up on this? I just received one from ebay with the wrong power supply and im hoping your story ended in good news

 

[SkywaveTDR]

Given enough time and spare parts, the units can be restored. Usually a regulator or some part blows or short and kills the voltage. The people with very high current sources will do the most damage.