Technics VX800 Extended Drive No Sound??

Thread Starter

richardh754

Joined Feb 4, 2022
13
Hi, the amp works fine normally but when the direct drive is pressed nothing happens?

I would like to fix this if possible
 

Thread Starter

richardh754

Joined Feb 4, 2022
13
Hi, I can solder and I have a meter i have fixed some cold solder joints on the transistors that got hot on it now the main amp works fine but no direct drive?
 

MisterBill2

Joined Jan 23, 2018
12,690
Hello! and welcome to the forum.
I am not familiar with this model and I wonder what is "direct drive" supposed to provide? How is that supposed to be different from that amplifier working?? If a relay is supposed to click but it does not, then the portion of the system controlling the relay is the place to check.
And now I am wondering about what other mode of operation a power amplifier can have besides direct drive.
 

MisterBill2

Joined Jan 23, 2018
12,690
OK, the very first thing to check is the switch that operates the relay that does the switch over. But if there is no relay then try switch cleaner, because it sounds like a switch problem.
AND, it also sounds like a rather useless feature, as I see it.
 

Thread Starter

richardh754

Joined Feb 4, 2022
13
yes, it sounds like a gimmik feature but my OCD wants everything working if I can, the switch is like a button switch, not a switch as such like the other models, when I press it the led light comes on but no sound or relay click
 

SamR

Joined Mar 19, 2019
4,334
Do you have the service manual? All it may need is a bit of deox spray on the switch or relay contacts.
 

MisterBill2

Joined Jan 23, 2018
12,690
It is more likely a failed switch contact. Sam is correct. I have fixed many tape machines with just a shot of contact cleaner on the Play/Record switch. That button drives a slider switch, most likely. And slider switches do get dirty contacts. You can also check and see if there is voltage being applied to the relay coil.
 

Thread Starter

richardh754

Joined Feb 4, 2022
13
Hi, took the front panal off, they were 6 resistors that had cold solder joints, done them now the relay works but still only a very faint sound when I press the extended direct drive button
 

abrsvc

Joined Jun 16, 2018
120
If you look at the service manual on page 21 (from the reference site listed above), you will notice that the relay causes the bypass of the tone amp section only. There is a 4570 IC in the tone amp section that may provide some level of pre-amp boost, but for the most part the sound level should be similar with the switch in either position. I would focus on the relays being bad.
Dan
 

LesJones

Joined Jan 8, 2017
3,773
What signal source do you have connected to the direct drive inputs ? My understanding is that this button only effects signals on the direct drive inputs. (See the fourth page of the service manual. Note the pages in the copy I found does not seem to have page numbers.)
 

Thread Starter

richardh754

Joined Feb 4, 2022
13
Hi, all fixed, it was the 6 risistors in the front panal that had cold soldered themselves, everything is working for now!!
 

MisterBill2

Joined Jan 23, 2018
12,690
Amazing how many problems can be caused by such a simple thing. I wonder if this one was hand soldered or wave soldered?
I suggest examining the rest of it for additional poorly soldered connections. Like the Kenwood amp that I repaired, poor soldering can be all over a device.
 
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