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


It is currently Apr Sun 05, 2020 4:25 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 16 posts ] 
Author Message
 Post subject: Zenith Royal 750 FREE Schematic Site Added
PostPosted: Feb Thu 06, 2020 9:34 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 4895
Location: Gainesville, Florida
is there such a thing as a PCB bottom layout? I have a schematic but locating the circuits on the traces is needed to troubleshoot an intermittent trouble. thanks for your help


Last edited by tubeAMP on Feb Sat 22, 2020 4:36 pm, edited 2 times in total.

Top
 Profile  
 
 Post subject: Re: Zenith Royal 750
PostPosted: Feb Thu 06, 2020 9:41 pm 
Member

Joined: Aug Wed 24, 2011 4:35 am
Posts: 4795
Location: Sunnyvale CA
tubeAMP wrote:
is there such a thing as a PCB bottom layout? I have a schematic but locating the circuits on the traces is needed to troubleshoot an intermittent trouble. thanks for your help


I will look when I get home, but I don't recall having anything like that.

This one is not nearly as prone as some of the smaller radios to cracked traces, but both of my Royal 750s have, bar-none, the worst PWB assembly workmanship I have every seen. One of them, I sucked and redid every single solder joint, because I just didn't trust it to keep working the way it was. Horrible gray blobby solder everywhere.

Brett


Top
 Profile  
 
 Post subject: Re: Zenith Royal 750
PostPosted: Feb Thu 06, 2020 10:05 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 4895
Location: Gainesville, Florida
thanks Bret for checking into it for me. thinking it was the headphone jack I tested with a head phone. it fails same time with the speaker so it must be internal. plays loud and clear then quits. sometimes fading. I tapped everything with a stick


Top
 Profile  
 
 Post subject: Re: Zenith Royal 750
PostPosted: Feb Thu 06, 2020 11:56 pm 
Member

Joined: Oct Mon 02, 2017 8:53 am
Posts: 399
Location: Panama City, FL 32401
I have the service manual for the 750,but unfortunately it doesn't show a bottom pinout. Also checked Radio Museum and no luck either. Sorry about that.


Top
 Profile  
 
 Post subject: Re: Zenith Royal 750
PostPosted: Feb Fri 07, 2020 12:34 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 4895
Location: Gainesville, Florida
I appreciate you checking Mr Zenith. thanks. what about top side component identification locations? RF, IF, driver, amp etc


Top
 Profile  
 
 Post subject: Re: Zenith Royal 750
PostPosted: Feb Fri 07, 2020 1:43 am 
Member

Joined: Oct Mon 02, 2017 8:53 am
Posts: 399
Location: Panama City, FL 32401
Attachment:
20190525_030021_resize_53.jpg
20190525_030021_resize_53.jpg [ 364.54 KiB | Viewed 962 times ]


This diagram is more legible than the others, which have tiny writing.


Top
 Profile  
 
 Post subject: Re: Zenith Royal 750
PostPosted: Feb Fri 07, 2020 3:23 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 4895
Location: Gainesville, Florida
that may help with the trace thanks


Top
 Profile  
 
 Post subject: Re: Zenith Royal 750
PostPosted: Feb Wed 19, 2020 8:29 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 4895
Location: Gainesville, Florida
success. I found the trouble but I dont have the schematic online to show you. I was checking C23 in the AVC circuit with an ohm meter when the radio started playing. I thought maybe the meter is supplying voltage that may be missing. there are two resistors in series to the battery. jumping one with 100k radio plays. soldered it underneath and radio is working great.
thanks for your concerns and assistance

https://radioattic.com/item.htm?radio=0520361


Top
 Profile  
 
 Post subject: Re: Zenith Royal 750
PostPosted: Feb Thu 20, 2020 7:40 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 4895
Location: Gainesville, Florida
I found this 750 schematic

https://elektrotanya.com/zenith_royal75 ... ad.html#dl


Top
 Profile  
 
 Post subject: Re: Zenith Royal 750 FREE Schematic Site Added
PostPosted: Feb Sun 23, 2020 5:01 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 422
Location: moreno valley
When recapping sometimes I hold the PC board up with a strong flashlight behind it to make sure I'm unsoldering the leads of the correct component, but it has to be one that lets light thru.


Top
 Profile  
 
 Post subject: Re: Zenith Royal 750 FREE Schematic Site Added
PostPosted: Feb Sun 23, 2020 5:21 am 
Member

Joined: Oct Mon 02, 2017 8:53 am
Posts: 399
Location: Panama City, FL 32401
frenchmarky wrote:
When recapping sometimes I hold the PC board up with a strong flashlight behind it to make sure I'm unsoldering the leads of the correct component, but it has to be one that lets light thru.



Same thing I do!


Top
 Profile  
 
 Post subject: Re: Zenith Royal 750 FREE Schematic Site Added
PostPosted: Feb Sun 23, 2020 7:32 am 
Member
User avatar

Joined: Jan Tue 31, 2012 1:55 am
Posts: 12012
Location: Mountains of Mourne. Ireland.
Zenith Royal 750L Chassis 8AT41Z2 was covered in Sams Photofact Set-438 Folder-17

A̶v̶a̶i̶l̶a̶b̶l̶e̶ ̶t̶o̶ ̶d̶o̶w̶n̶l̶o̶a̶d̶ ̶f̶r̶o̶m̶ ̶r̶a̶d̶i̶o̶m̶u̶s̶e̶u̶m̶.̶o̶r̶g̶
B̶o̶t̶t̶o̶m̶ ̶s̶i̶x̶-̶p̶a̶g̶e̶s̶ ̶i̶n̶ ̶t̶h̶e̶ ̶r̶i̶g̶h̶t̶/̶h̶a̶n̶d̶ ̶s̶c̶r̶o̶l̶l̶i̶n̶g̶ ̶w̶i̶n̶d̶o̶w̶,̶ ̶h̶e̶r̶e̶...
https://www.radiomuseum.org/r/zenith_royal_750l.html

The Sams can be found here, in zipped folder...
https://childhoodradio.com/download/zen ... h-8at41z2/

Image
Large image→ https://i.ebayimg.com/images/g/isgAAOSw ... -l1600.jpg

$9.99 shipped, eBay https://www.ebay.com/itm/274212554888

Greg.


Zenith Royal 750 employs chassis 8AT41
Chassis 8AT41Z2 images... viewtopic.php?f=4&t=308338


Top
 Profile  
 
 Post subject: Re: Zenith Royal 750 FREE Schematic Site Added
PostPosted: Feb Sun 23, 2020 2:34 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 4895
Location: Gainesville, Florida
plenty of schematics now :D

thats funny. the childhood schematic is totally different than the one I have. same model number same chassis number. R13 is 180k. the diagram I used says 100k. no wonder it is so loud

I used a flashlight to see through the board and replace a 100k in the AVC circuit. radio instantly changed from not working to working. I should put a 180k in there. it is too loud with 100k. I have a 200k. that should do it


Top
 Profile  
 
 Post subject: Re: Zenith Royal 750 FREE Schematic Site Added
PostPosted: Feb Tue 25, 2020 1:12 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 4895
Location: Gainesville, Florida
I decided to replace the 100k with 200k in the AVC circuit. seems like it is not blasting roaring loud anymore but plenty of volume :shock:


Top
 Profile  
 
 Post subject: Re: Zenith Royal 750 FREE Schematic Site Added
PostPosted: Feb Tue 25, 2020 10:57 am 
Member
User avatar

Joined: Jan Tue 31, 2012 1:55 am
Posts: 12012
Location: Mountains of Mourne. Ireland.
Photofact Set-438 Folder-17 was published in April of 1959
The service data that you have downloaded is from Sams TSM-4 (transistor radio series) which was published in October of the same year.

Running changes aka revisions - component substitution and circuit improvements are not uncommon on long production runs.

Greg.


Top
 Profile  
 
 Post subject: Re: Zenith Royal 750 FREE Schematic Site Added
PostPosted: Feb Tue 25, 2020 3:18 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 4895
Location: Gainesville, Florida
I was wondering why the two diagrams were so different. I thought that I was seeing a faded resistor in the circuit but it looks like it really was 180k. thanks Greg


Top
 Profile  
 
Post New Topic Post Reply  [ 16 posts ]  Moderator: Dave Doughty

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 6 guests



Search for:
Jump to:  


































-->


Privacy Policy :: Powered by phpBB