Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives :: Books
Support This Site: Contributors :: Advertise


It is currently Aug Thu 17, 2017 9:03 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 431 posts ]  Go to page 1, 2, 3, 4, 5 ... 22  Next
Author Message
 Post subject: marconi model 160
PostPosted: Sep Sat 17, 2016 9:42 pm 
Member

Joined: Mar Fri 07, 2014 10:20 am
Posts: 1625
i have a Marconi model 160 that I just sent away to be repaired and had a new transformer installed and when I got it back the 5y4g tube was the only one to light and it has no dc voltage on any of the tubes and no I will not send it back to the shop any help will be great thanks a0e 1k0 nl


Top
 Profile  
 
 Post subject: Re: marconi model 160
PostPosted: Sep Sat 17, 2016 9:57 pm 
Member

Joined: Dec Sat 24, 2011 9:17 pm
Posts: 1081
Location: Vancouver Island, Canada
More info please.
We know it is a transformer set, 8 tubes with a 6F6 power tube.

Which transformer was replaced? Should we assume it was the power transformer? Because that is where your trouble seems to be.

We know the primary of the main power transformer is connected as the rectifier is receiving its 5 volts.
There are multiple connections to the secondary side of a typical power transformer. One winding provides 6.3 volts for the heaters of the other tubes. A high voltage winding provides the B+. That winding should give you a high voltage reading across pins 3 and 5 of the rectifier tube.

Sometimes if there is a problem with one of the heater windings, a small transformer is added to replace the dead winding. Not enough info to go by here.

_________________
It's her famous spinach and feta cheese salad. I never get thick of it.
[:l>)


Top
 Profile  
 
 Post subject: Re: marconi model 160
PostPosted: Sep Sat 17, 2016 10:02 pm 
Member

Joined: Mar Fri 07, 2014 10:20 am
Posts: 1625
yes it was the power transformer and it is a new one and I am getting no voltage at all on all the other tubes


Top
 Profile  
 
 Post subject: Re: marconi model 160
PostPosted: Sep Sat 17, 2016 10:49 pm 
Member

Joined: Mar Fri 07, 2014 10:20 am
Posts: 1625
the only voltage I get is on pin 5 of tube 5y4g and it is 335 ac volts


Top
 Profile  
 
 Post subject: Re: marconi model 160
PostPosted: Sep Sun 18, 2016 1:23 am 
Moderator
User avatar

Joined: Feb Sun 01, 2009 2:56 pm
Posts: 8746
Location: Victoria, Australia
+1 on more info. However, I would like to see the rectifier removed then confirm the AC volts on all of its socket pins. Pins 7 & 8 will have the 5V (Across them). Pins 3 & 5 relative to chassis the 355V which is indeed AC.

DC comes off of pins 7 & 8 but only with the rectifier fitted & working. It may pay to remove the wire taking off the DC from the filaments to check & ensure that the 5V winding is not grounded. I have seen that happen with cut insulation & it flashed over as soon as there was B+.

This does not bode well as a quality job; you are going to have to check everything.

Marc


Top
 Profile  
 
 Post subject: Re: marconi model 160
PostPosted: Sep Sun 18, 2016 3:29 am 
Member
User avatar

Joined: Aug Tue 19, 2014 8:08 pm
Posts: 453
Location: Dallas, TX USA
Here is the schematic, from http://radio.codegods.ca/node/6625 :
Attachment:
IMG_0698.JPG
IMG_0698.JPG [ 220.05 KiB | Viewed 1944 times ]

Attachment:
IMG_0699.JPG
IMG_0699.JPG [ 156.39 KiB | Viewed 1944 times ]

_________________
Please see my profile for alternate schematic sites.


Top
 Profile  
 
 Post subject: Re: marconi model 160
PostPosted: Sep Sun 18, 2016 3:39 am 
Member

Joined: Dec Sat 24, 2011 9:17 pm
Posts: 1081
Location: Vancouver Island, Canada
You have 5 volts, 5Y4 lights up, and you measured 355 vac on pin 5, so two of the secondary windings are probably correctly connected to the right tube socket pins.
The secondary winding that supplies 6.3 volts to the heaters of the other tubes is not connected or the new transformer is faulty.
You are looking for wires that do not go to the rectifier tube socket. They are color coded, so give us the colors and tell us where they go.

_________________
It's her famous spinach and feta cheese salad. I never get thick of it.
[:l>)


Top
 Profile  
 
 Post subject: Re: marconi model 160
PostPosted: Sep Sun 18, 2016 5:27 am 
Moderator
User avatar

Joined: Feb Sun 01, 2009 2:56 pm
Posts: 8746
Location: Victoria, Australia
I note now that we have a schematic that the unused socket pins of the 5Y4 have become tags of convenience. Its fine to have power chassis to pin 5 but where's the other half of the CT winding that is supposed to be on pin 3? What was whoever you sent the radio too, supposed to be doing to it? It is looking like a shemozzle leave the rectifier out until you identify all of the groupings of the windings.

An ohm meter on pin 5 should find the rest of the High voltage secondary unless its open or does not exist.

Marc


Top
 Profile  
 
 Post subject: Re: marconi model 160
PostPosted: Sep Sun 18, 2016 11:56 am 
Member

Joined: Mar Fri 07, 2014 10:20 am
Posts: 1625
sorry I was so mad with the guy who repaired the radio the voltage I checked was on pin 5 of the 6f6 tube next to tube 5y4 not tube 5y4 and the wires from the transformer will follow


Top
 Profile  
 
 Post subject: Re: marconi model 160
PostPosted: Sep Sun 18, 2016 12:08 pm 
Member

Joined: Mar Fri 07, 2014 10:20 am
Posts: 1625
looking at the transformer from bottom left side it has 2 yellow wires, and one yellow with a green stripe and a green with yellow stripe. First one yellow and orange from other side goes to chassis ground , the other yellow goes to pin 1 of 5y4 , the yellow and green goes to pin 7 of 5y4 and the green with yellow stripe is not attached. The other side has a blk wire attached to power cord, a blue wire not attached , a brown wire attached to on off button opposite power cord pin, a grey wire not attached and two red wires going to pins 3 and 5 of tube 5y4.


Top
 Profile  
 
 Post subject: Re: marconi model 160
PostPosted: Sep Sun 18, 2016 12:20 pm 
Member

Joined: Mar Fri 07, 2014 10:20 am
Posts: 1625
the transformer is a Pt275.2 usa power transformer tube audio 275-0-275x100ma input blk-blu 115v ac or blk-brn 120vac hivoltage red 275vac org ct red 275vac 100ma gry-org55vac htr1 yel-yel 6.3vac 3a htr2 yel-yel/grn 5vac grn-grn/yel 6.3vac 2a


Top
 Profile  
 
 Post subject: Re: marconi model 160
PostPosted: Sep Sun 18, 2016 12:45 pm 
Moderator
User avatar

Joined: Feb Sun 01, 2009 2:56 pm
Posts: 8746
Location: Victoria, Australia
This seems to be going to hell in a hand basket: What have these clowns done? You do not get AC on tubes past the rectifier without a serious stuffup. Secondly if that was DC on Pin 5 of a 6F6, Pin5 is the control grid; -24 to -26 yes the only time that you would get that voltage on G1, which should be DC is if the cathode is open to ground. I wonder where they put the HV Centre tap?

It looks like I may have been on the right track & would expand on it: You are going to have to start at the utility power point and check every bit of it from wiring to component values.

Marc


Top
 Profile  
 
 Post subject: Re: marconi model 160
PostPosted: Sep Sun 18, 2016 2:13 pm 
Member

Joined: Mar Fri 07, 2014 10:20 am
Posts: 1625
That being said what is step one for me thanks other then ask for my 250 dollars back from the guy who made the mess


Top
 Profile  
 
 Post subject: Re: marconi model 160
PostPosted: Sep Sun 18, 2016 3:46 pm 
Moderator
User avatar

Joined: Feb Sun 01, 2009 2:56 pm
Posts: 8746
Location: Victoria, Australia
Getting the money back would be a good start especially if it isn't a goer & its a mess. Did he ever make the claim that he fixed it? Then it comes down to competency. If you get the coin back you have choices.

One is to fix it yourself and the other to find someone that can and that in both cases requires the competence the other clown hasn't got. As I have indicated, you start with the power supply part. But there are a few things to check, like the speaker transformer. If you crack a 9V battery across its primary (pins 3&4 of the 6F6) you hopefully get sound. If not you investigate that as you will never fix it with no sound reproducer working.

Before you even touch anything, even that it is possibly wrong, photograph the inside of the pan. Sharp, clear, pics; Do not get too close especially with a flash and depth of field suffers as well. You may need to scrap the auto focus and focus on something in the middle between chassis top & bottom: You can crop it later if its digital. Then you have to decide if you can understand the schematic and extrapolate the info to that which is in the chassis, before starting on tracing everything in the correct order viz: Power, Audio, IF, front end & when its all sorted & works align it.

There's a bit of work to be done before even contemplating powering it again, so forget fixing it quickly.

Marc


Top
 Profile  
 
 Post subject: Re: marconi model 160
PostPosted: Sep Sun 18, 2016 6:15 pm 
Member

Joined: Mar Fri 07, 2014 10:20 am
Posts: 1625
checked the speaker on tube 6f6 and is fine now is there a way to check the power transformer because it has a hum in it thanks


Top
 Profile  
 
 Post subject: Re: marconi model 160
PostPosted: Sep Sun 18, 2016 6:45 pm 
Member

Joined: Mar Fri 07, 2014 10:20 am
Posts: 1625
the dc voltage on tube 5y4 on pins 7 and 8 is 335 and the ac voltage on pins 3 and 5 is 276 is this good ? I so what next should I do?


Top
 Profile  
 
 Post subject: Re: marconi model 160
PostPosted: Sep Sun 18, 2016 6:47 pm 
Member

Joined: Mar Fri 07, 2014 10:20 am
Posts: 1625
the dc voltage on tube 5y4 on pins 7 and 8 is 335 and the ac voltage on pins 3 and 5 is 276 is this good ? I so what next should I do?


Top
 Profile  
 
 Post subject: Re: marconi model 160
PostPosted: Sep Sun 18, 2016 7:07 pm 
Member

Joined: Mar Fri 07, 2014 10:20 am
Posts: 1625
also why do I have 6.3 ac volts on pin 1 of tube 5y4 and this is the wire direct from transformer and the pinout shows 0 v for pin 1


Top
 Profile  
 
 Post subject: Re: marconi model 160
PostPosted: Sep Mon 19, 2016 1:15 am 
Moderator
User avatar

Joined: Feb Sun 01, 2009 2:56 pm
Posts: 8746
Location: Victoria, Australia
What I am seeing is clear evidence of a major stuffup, or incorrect reading of the base. The transformer is probably growling because of a short. I am attaching the pinout for an octal socket looking at it from the wiring side. Identify all windings on the transformer: Then we need to establish what they are connected too, as opposed to what they should be connected to.

Most octals (note not all) have pins 2 & 7 as the heater: Commonly one of which will be grounded that also applies to pin one of a metal and that pin should not be used for anything else.

Only four pins of the rectifier are used by it. The rest are quite often used as nodes / tags of convenience, for other things Pins 3, 5, 7 & 8. are the ones that have to be absolutely correct.

For 6F6...
Pin 1 = Shield if metal; NC glass
Pin 2 = Heater
Pin 3 = Anode: Speaker transformer primary (Perhaps tone) & a bypass cap
Pin 4 = Screen (g2) B+ usually directly on it
Pin 5 = Control grid (g1) -24V -28V Push pull
Pin 6 = NC
Pin 7 = Heater
Pin 8 = Cathode (k) and Suppressor (g3)

Marc


Attachments:
IO.jpg
IO.jpg [ 9.95 KiB | Viewed 1858 times ]
Top
 Profile  
 
 Post subject: Re: marconi model 160
PostPosted: Sep Mon 19, 2016 4:41 pm 
Member

Joined: Dec Sat 24, 2011 9:17 pm
Posts: 1081
Location: Vancouver Island, Canada
spsquires wrote:
also why do I have 6.3 ac volts on pin 1 of tube 5y4 and this is the wire direct from transformer and the pinout shows 0 v for pin 1
What Marc said.
Pin 1 of the 5Y4 is simply a tie point, because it is convenient to the transformer. No connection (NC) to the rectifier circuit. Another wire or wires carries the 6.3 volts to the heaters of the rest of the tubes. So on paper, 0 v, but in your radio, 6.3 v enroute elsewhere. You may have a poor connection right there. Trace that other wire to its other end and take a voltage measurement. If it is 0 volts AC, you found a fault.

From what you say in previous posts, you may be confusing the pin locations in your voltages checks.
Avoid powering up the set for more than a few minutes. Use a power bar with an on/off switch. Use alligator clips to attach the meter, sit back, apply power briefly.

_________________
It's her famous spinach and feta cheese salad. I never get thick of it.
[:l>)


Top
 Profile  
 
Post New Topic Post Reply  [ 431 posts ]  Moderators: Marcc, Norm Leal Go to page 1, 2, 3, 4, 5 ... 22  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 15 guests



Search for:
Jump to:  




















Privacy Policy :: Powered by phpBB