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 Post subject: Need Schematic for Grundig RF80U
PostPosted: Feb Tue 18, 2020 3:42 am 
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Joined: Mar Thu 02, 2017 1:37 am
Posts: 605
Location: Cedar Rapids, Iowa
I picked up a Grundig RF80U on eBay this morning and have been unable to find any documentation for it on line. Can someone help me out?

Thanks!

Rich


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 Post subject: Re: Need Schematic for Grundig RF80U
PostPosted: Feb Tue 18, 2020 8:28 am 
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Joined: Jul Tue 03, 2012 9:20 am
Posts: 15
The set is similar to RF110.

https://www.radiomuseum.org/r/grundig_rf110_rf_110.html

Greetings from Germany,
Werner


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 Post subject: Re: Need Schematic for Grundig RF80U
PostPosted: Feb Tue 18, 2020 3:04 pm 
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Joined: Mar Thu 02, 2017 1:37 am
Posts: 605
Location: Cedar Rapids, Iowa
Thanks Werner. Yes, when I was looking at Grundig pictures on RadioMuseum looking for my new radio, I thought it was an RF110 at first because they look identical. But then I noticed that the RF110 has a long wave band so kept looking until I found the RF80U. If I can't find documentation for the RF80U I'll use the RF110 schematic, but still looking for the correct one.

Thanks!

Rich


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 Post subject: Re: Need Schematic for Grundig RF80U
PostPosted: Feb Tue 18, 2020 8:54 pm 
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Location: Mountains of Mourne. Ireland.
As Werner says, nine-transistor RF110 uses the same circuit-board as your Portuguese radio.
There will be some component differences.
Service manual: http://www.philipsradios.nl/Schemas/ove ... 0RF110.pdf
Printer friendly: https://www.doctsf.com/grundig-rf-110-a ... f30498/o=y

Matt aka 50sTransistorRadios had one a while back...
https://www.youtube.com/watch?v=27ZKH_ZZVTQ

memberlist.php?mode=viewprofile&u=25077

Greg.


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 Post subject: Re: Need Schematic for Grundig RF80U
PostPosted: Feb Tue 18, 2020 11:28 pm 
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Joined: Mar Thu 02, 2017 1:37 am
Posts: 605
Location: Cedar Rapids, Iowa
Thanks Greg! I did find that video when I did my searching yesterday and watched it. Thanks for looking up his profile for me ;)

Rich


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 Post subject: Re: Need Schematic for Grundig RF80U
PostPosted: Feb Wed 19, 2020 1:34 am 
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Joined: Sep Sat 29, 2012 6:32 pm
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Location: 13760
Rich,
Alas, I sold that radio, and the documentation for it, back at the last Kutztown meet I attended (May 2017).
Unfortunately, I didn't scan in the documentation before I sold it, so that video Greg linked is all I have left of it.
Thankfully though, I see I did at least show the schematic fairly clearly towards the end of the video, hopefully that helps!
-Matt


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 Post subject: Re: Need Schematic for Grundig RF80U
PostPosted: Feb Wed 19, 2020 1:53 pm 
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Joined: Jul Wed 22, 2009 3:07 pm
Posts: 814
Hello Everyone,

I am just wondering if that radio also had an AM only version?
The RM web-site lists that radio only having six transistors, and I do not see how a decent AM-FM radio can be made with so few transistors (and no ICs):
https://www.radiomuseum.org/r/grundig_rf80u.html
Interestingly, the picture, and the specs, show an AM-FM radio...

Peter


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 Post subject: Re: Need Schematic for Grundig RF80U
PostPosted: Feb Thu 20, 2020 1:06 am 
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Location: Mountains of Mourne. Ireland.
Peter, there has been many errors on radiomuseum.org over the years. Generally they do a good job.
Schematic errors are not uncommon too.

Rich may provide some photos of the chassis when he wakes up... :)
Greg.


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 Post subject: Re: Need Schematic for Grundig RF80U
PostPosted: Feb Thu 20, 2020 2:03 am 
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While I only count 6 transistors on the portion of the schematic visible in my video (I try to do a better job of showing such things clearly these days), they are numbered up to 9. I suspect the transistors in the FM front end didn't get counted in radiomuseum's total.


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 Post subject: Re: Need Schematic for Grundig RF80U
PostPosted: Feb Thu 20, 2020 3:35 pm 
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Joined: Mar Thu 02, 2017 1:37 am
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Location: Cedar Rapids, Iowa
egg wrote:
Rich may provide some photos of the chassis when he wakes up... :)
Greg.

While wake-up time is always an issue for me :P in this case the main issue is radio arrival date. According to the post office it should arrive Tuesday. Then memory will become the issue. I'll try to remember to post some photos.

Rich


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 Post subject: Re: Need Schematic for Grundig RF80U
PostPosted: Feb Sun 23, 2020 7:07 pm 
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Joined: Mar Thu 02, 2017 1:37 am
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Location: Cedar Rapids, Iowa
The RF80U came in yesterday. I count 7 transistors...4 on the main board (circled in blue), 1 in the large can oriented vertically (detector circuit?), and 2 in the FM can.

I thought this was going to be a lost cause when I opened it up and saw this:
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But it looks like that is just a coil that is attached to the side of the ferrite rod and couples the external antenna to the ferrite rod (circled in red). I was able to remove it and get in untangled, so I'll just cut off the wires that unraveled and it should be ok. There are many bare spots in the unraveled sections so there is no use trying to rewind.

Someone has been in here doing some work. It's hard to see in the photo, but the connection circled in yellow is floating in mid-air. I don't think Grundig would do something like that :P so I'll have to figure out what to do about it.

This radio was listed as not working, but when I powered it up it worked. The volume control needed cleaning but AM works decent and FM works, but the volume is way low, so it will need some work.

The board isn't identical to the RF110, but it's close, so that manual should help.

Rich


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main_board_rear_001_r.jpg
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 Post subject: Re: Need Schematic for Grundig RF80U
PostPosted: Feb Mon 24, 2020 4:32 am 
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Joined: Mar Thu 02, 2017 1:37 am
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Location: Cedar Rapids, Iowa
I'm going to have to amend this. The output transistors are mounted on the heat sink on the right side of the board, so there are 9 total transistors.

Rich


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 Post subject: Re: Need Schematic for Grundig RF80U
PostPosted: Feb Tue 25, 2020 4:38 pm 
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Joined: Mar Thu 02, 2017 1:37 am
Posts: 605
Location: Cedar Rapids, Iowa
For anyone that finds this thread looking for RF80U information, I've attached a schematic of the RF110 that has been marked to show parts that are not in the RF80U, marked with a red 'X'. I also found two part value differences that I've marked on the schematic (R13 and C1 in the F111 can). I believe this is complete and accurate, but can't guarantee it. In some cases the part just isn't there, in other cases it's been replaced by a wire.

I've tested all of the resistors, including lifting those that needed to be tested out of circuit, and every single resistor is well within tolerance. Very impressive.

After a good cleaning of the volume control and the bandswitch both AM and FM are working well so I'm debating whether or not to do the recap. I'll do all of the electrolytics, but haven't decided about the paper caps. All I have are the yellow axial lead film caps and I think it would look a little silly with a bunch of them standing on end with the top lead bent over to go through the board. I'm going to tinker with printing some casings on the 3D printer and see what that looks like. Any other suggestions?

EDIT (20200227) - Removed the original attachment attached a new version in my post on February 27th...see below.

Thanks!
Rich


Last edited by criageek on Feb Thu 27, 2020 3:15 pm, edited 1 time in total.

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 Post subject: Re: Need Schematic for Grundig RF80U
PostPosted: Feb Thu 27, 2020 12:16 am 
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Joined: Mar Thu 02, 2017 1:37 am
Posts: 605
Location: Cedar Rapids, Iowa
I'm hoping a moderator can help me out here. I found 2 mistakes in the pdf I attached earlier showing parts that are not in the RF80U on the RF110 schematic. I don't want to clutter up the forum by posting it again. Can I get the previous one deleted so I can post the new one? Or perhaps I can send the new one to a mod and they can replace it?

Thanks,
Rich


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 Post subject: Re: Need Schematic for Grundig RF80U
PostPosted: Feb Thu 27, 2020 7:58 am 
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Location: Mountains of Mourne. Ireland.
You can edit any of your postings when logged-in.
Edit "radio-button" at bottom/right of post.

Greg.
oh... you can also edit/change the title of your thread by editing your first post.


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 Post subject: Re: Need Schematic for Grundig RF80U
PostPosted: Feb Thu 27, 2020 3:17 pm 
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Joined: Mar Thu 02, 2017 1:37 am
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Location: Cedar Rapids, Iowa
Thanks Greg - I had not tried that because I KNOW I read a thread in just the last few weeks that said the editing rules had changed and you could only edit within an hour of posting. Maybe that was just in certain categories? Anyway, I've removed the original attachment and attached the new updated version here.

Thanks,
Rich


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Grundig RF110_marked_for_RF80U.pdf [1.26 MiB]
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 Post subject: Re: Need Schematic for Grundig RF80U
PostPosted: Feb Fri 28, 2020 3:52 pm 
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Joined: Mar Thu 02, 2017 1:37 am
Posts: 605
Location: Cedar Rapids, Iowa
Just a quick update on this radio and a couple of observations. I've removed and tested all but 4 (those four are in tough-to-get-to places) of the paper (I'm calling them paper but don't know if they are actually paper) caps and every one of them was spot on for value and measured no leakage, so I will not be replacing any of them. I found no leakage in any of the electrolytics as well, and most measured right on for value...3 were more than 20% high. I'm thinking I'll probably replace all the electrolytics. I will check the alignment but if it's close I won't mess with it. I'll also check the bias on the output transistors and adjust if necessary.

A couple of observations for anyone working on this or a similar radio. First, it's quite easy to lift or damage pads or traces on the circuit board so use caution. I started using my solder sucker at an angle as opposed to straight on and had no issue after that.

Second, I think the paper caps are marked for the outside foil...mostly with a small line, but others with a small symbol (didn't get a picture of that)
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Then the board is marked with a circle on one lead to indicate where the foil side should go.
Attachment:
paper_cap_002_r.jpg
paper_cap_002_r.jpg [ 108.4 KiB | Viewed 772 times ]
This may or may not be accurate because I did find at least one that didn't adhere to this pattern. I generally test the caps to find the foil side and reinstall the 'proper' way. I know there are arguments on both sides as far as the necessity of doing this, but I figure it doesn't hurt anything, just takes a little extra time.

Rich


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 Post subject: Re: Need Schematic for Grundig RF80U
PostPosted: Feb Fri 28, 2020 9:27 pm 
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Location: Mountains of Mourne. Ireland.
C57 et al.

Those are Polyester film-capacitors, designated KT on the schematic's capacitor legend/chart.

KS are Polystyrene capacitors.
Apart from the Electrolytics, the others are Ceramic and Tantalum.

Film capacitors type abbreviations.
Just over halfway down this page.
https://en.wikipedia.org/wiki/Film_capacitor

Greg.


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 Post subject: Re: Need Schematic for Grundig RF80U
PostPosted: Feb Fri 28, 2020 9:50 pm 
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Joined: Jan Tue 31, 2012 1:55 am
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Location: Mountains of Mourne. Ireland.
This is a great site for German to English (technical words) translation, where examples of sentences are shown in both languages.

E.g. kunststoffgehäuse
https://www.linguee.com/german-english/ ... A4use.html

Greg.


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 Post subject: Re: Need Schematic for Grundig RF80U
PostPosted: Feb Fri 28, 2020 9:58 pm 
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Joined: Mar Thu 02, 2017 1:37 am
Posts: 605
Location: Cedar Rapids, Iowa
Thanks Greg! I did translate Kondensatoren using https://www.deepl.com/translator, which just means capacitors. I didn't know where to find out what KS and KT meant.

Rich


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