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 Post subject: 1957 Grundig 5088
PostPosted: Jan Sun 02, 2011 8:14 pm 
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Nobody on this forum ever told me once I got one old radio, I would have the insatiable urge to get more!

But I digress...

I just acquired a Grundig 5088 that was reported to be in good working condition. As received the cabinet appeared to be in great condition, with a few minor scuffs.

Image

The original (and hard to find) EL35 tuning eye glows brightly and works as intended

Image


The seller told me that me that he used it recently and that there way no problems with it. Taking that with a grain of salt I checked the chassis to make sure there weren't any rotten old main filter caps installed. It looks like the chassis was partially recapped as there were new looking filter caps as well as an orange drop and a couple yellow tube caps.

So I powered it up with my hand on the plug ready to kill power at the first sign of trouble. After the tubes warmed up, I was rewarded with some pretty good reception and sound quality. I removed the chassis and found nothing strange. One dial cord was strung incorrectly, the ferrite antenna was stuck in place and there was general grime on things. Cleaning, oiling, and polishing took care of those and its 95% from being ready for full time action.

I found it odd that at some point it had been recapped, but there appeared to be several original paper caps left in place. Are these the German cousins to American made now unreliable paper/wax caps?

Image

Are the caps in the red arrow micas or ceramic or are they paper/wax ones that need to be replaced. The one in the blue arrow looks more like a paper one that I will buy buying a replacement for.

Image

Is there anything else I need to watch out for on this radio? Under close watch it played for 30 minutes with no problem, but with a little occasional crackle from the speaker, probably from the old paper caps still in there.

Thanks

--
John


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 Post subject:
PostPosted: Jan Sun 02, 2011 8:24 pm 
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I would plan on replacement of all those caps. they are paper, just european made. most will leak or be outright bad.
There will be a boatload of them... stock up !

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 Post subject:
PostPosted: Jan Sun 02, 2011 9:04 pm 
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Location: Shiner ,Texas
If you have not already seen the excellent discussion at Radiomuseum on this model....excellent info...http://www.radiomuseum.org/forum/grundi ... .........I stocked up years ago on NOS selenium rectifiers ...these also go bad .


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 Post subject:
PostPosted: Jan Sun 02, 2011 9:29 pm 
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That is one of the largest table models they made and they sound great. I have one that I want to get started on soon. I have found those brown caps to be leaky so I would replace all of them.


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 Post subject:
PostPosted: Jan Sun 02, 2011 10:28 pm 
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Thing of beauty!!!

Happy New Year
Steve

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 Post subject:
PostPosted: Jan Sun 02, 2011 10:29 pm 
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Lose the WIMA brown capacitors. The little
beauties paid my rent bought me food 50 years
ago!

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 Post subject:
PostPosted: Jan Sun 02, 2011 11:16 pm 
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While it's out of the cabinet, you may want to service all the mechanical selector switches and tone equalization controls that this set uses.

There are a lot of them, and they will benefit from some contact cleaner and selective lubrication of the key linkage mechnanism.

That's a great looking set and I am guessing it will sound excellent when you are finished.

I have it's cousin, the 5060a.

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 Post subject:
PostPosted: Jan Sun 02, 2011 11:47 pm 
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Location: Colorado Springs, CO
As for the types of the caps:
The German-language schematic for my 3395 has a different symbol for each type of cap, with a decoder key: I.e. "250V paper", etc. There were some paper, some 'styroflex', and some ceramic. Five types all together. Also 5 types of resistors (1/4, 1/3, 1/2, 1, and wirewound).

Mine had paper caps coupled to high-value grid-leak resistors (22 megs on the 1st audio grids!). Seems like a bad design choice to me - and the cap seems like an unnecessarily large value: 0.022uF coupling to a 22M resistor and a triode grid - I think a much smaller value would work just as well, but I used a 0.02uF anyway.
And one of those coupling caps was a special shielded type (has a 3rd wire coming out, tied to ground). I replaced it with a ceramic, but connected it with a short length of coax cable where it runs near other signals.

I didn't replace *all* the papers in mine, just the ones that are in "important" parts of the circuit, such as the coupling into the 1st and 2nd audio grids.

Pete


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 Post subject:
PostPosted: Jan Mon 03, 2011 12:05 am 
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Location: Malone, New York USA
I'd replace *all* the paper "ERO" and "WIMA" capacitors.
All are important- just some are more immediately critical to operation than others.
Suggest to decide if this is a historic piece to be preserved for posterity and study, or a neat example of tube technology to be played and enjoyed.
If the latter, it is prudent and not exactly earth-shaking financially to replace the leaky caps.
To do less is akin to washing half your face.

saipan59 wrote:
(has a 3rd wire coming out, tied to ground). I replaced it with a ceramic,

Ceramic caps for audio? I thought they could cause "ringing."

Is that 5088 tuned to a really strong station? The tuning eye appears fully closed as it would with a Soviet 6E5S/c. I've never had an EM34 or 35 fully closed unless I was pushing a strong signal through a signal generator....Of course- I ain't seen it all yet..


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 Post subject:
PostPosted: Jan Mon 03, 2011 12:48 am 
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Dennis Daly wrote:
saipan59 wrote:
(has a 3rd wire coming out, tied to ground). I replaced it with a ceramic,

Ceramic caps for audio? I thought they could cause "ringing."

It was originally a 0.022uF 250V paper; I replaced it with a good-quality 0.02uF 1kV ceramic. It is more than good enough.
I'm sure there are some golden-ear folks that would claim a 0.00005% difference in sound quality... ;-)
OTOH, the ceramic has less inductance than most other options, so maybe *I* can claim "better sound quality"...

Pete


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 Post subject:
PostPosted: Jan Mon 03, 2011 1:20 am 
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Location: Shiner ,Texas
I also noticed the closed tuning eye...have one on my Graetz and 4010w Grundig...they should not close completely..something is amiss Dr.Watson...well the radio shows both available..I know the EM34 has a two fan fold display that never closes completely..the EM35 has a split into quarters display that has a coarse tuning display on two quarters and when you get real close to the best signal the other two quarters kick in tighter...a progessive closing..that does get real tight.... upon closer examination I can see a quartered display....I deduce I am looking at an EM35.


Last edited by Sperrkreis on Jan Mon 03, 2011 2:28 am, edited 2 times in total.

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 Post subject:
PostPosted: Jan Mon 03, 2011 1:24 am 
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Location: Latham NY
I thought that set used the EM-34?


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 Post subject:
PostPosted: Jan Mon 03, 2011 3:34 am 
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According to RMorg, it could use either an EM34 or EM35.
Yeah---I also noticed, after staring long enough at the photo, what _appears_ to be maybe???- the four sectors of an EM35 tube......What is still puzzling to me is that the display is fully closed- as I mentioned above...IF it is indeed an EM35 tube.
To find a radio like this with a yet-bright EM35 tube is, (or would be,) a rare (and lucky) find.
(I'm not envious...I've been blessed with sufficient quantities of both types.)


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 Post subject:
PostPosted: Jan Mon 03, 2011 6:16 pm 
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Joined: Jun Fri 04, 2010 6:25 am
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Location: Sacramento/San Francisco
Hello all,

Thanks for the replies!

The tuning eye is NOT all the way closed. It is a photo graphical error, the eye never fully closes, it get pretty close but never there. I did not note specifically which eye tube it was. I was reading off of the back panel which said "EM34/35"

I have removed the chassis and done a pretty good job of cleaning and lubricating all the little moving parts and it responded very nicely to it.

I will go ahead and replace all the caps. It wont be too expensive and there are half of them already been changed. It will only improve the audio and make it more stable.

Also I think my set still has the selenium rectifiers. There is a tall narrow can on the chassis almost right off the power supply. What do I replace those with?

Thanks.

--
John


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 Post subject:
PostPosted: Jan Mon 03, 2011 6:54 pm 
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Location: Malone, New York USA
jrogosich wrote:
Also I think my set still has the selenium rectifiers. There is a tall narrow can on the chassis almost right off the power supply. What do I replace those with?


A bunch of us could banter re: the rectifier replacement- and argue among ourselves re: the virtue of doing so as a precaution.

Is B+ output low and the can feels hot to the touch when running? Or, is the can just tepid and the B+ voltage within 10% of spec after it operates for a few hours?
That can be just a couple of deciding factors to replace or leave alone.....
but.....Nothing like getting some of the how-to "scoop" from Mr. Hans Knoll himself. His English is not perfect, (neither is my German,)- but when it comes to German radio engineering and design, he's one of the best. (Engineering lab tech for Grundig when these radios were built.)
http://www.radiomuseum.org/forum/grundi ... tions.html

Some like an elegant build of a silicon bridge using perf board and installed back in the black can housing.....Others may argue using snubbers or not as necessary in this type circuit.....I suggest about 100 ohms@ 5-10 watts (for this particular model) in the negative lead (in lieu of the wire jumper to chassis ground) after silicon replacement. This to provide voltage drop not created with replacement silicon vs. original selenium unit.

Great re: the photo anomaly of the EM35....We can rest easy now. :)


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 Post subject:
PostPosted: Jan Mon 03, 2011 9:21 pm 
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Quote:
A bunch of us could banter re: the rectifier replacement- and argue among ourselves re: the virtue of doing so as a precaution.

Is B+ output low and the can feels hot to the touch when running? Or, is the can just tepid and the B+ voltage within 10% of spec after it operates for a few hours?
That can be just a couple of deciding factors to replace or leave alone.....
but.....Nothing like getting some of the how-to "scoop" from Mr. Hans Knoll himself. His English is not perfect, (neither is my German,)- but when it comes to German radio engineering and design, he's one of the best. (Engineering lab tech for Grundig when these radios were built.)
http://www.radiomuseum.org/forum/grundi ... tions.html

Some like an elegant build of a silicon bridge using perf board and installed back in the black can housing.....Others may argue using snubbers or not as necessary in this type circuit.....I suggest about 100 ohms@ 5-10 watts (for this particular model) in the negative lead (in lieu of the wire jumper to chassis ground) after silicon replacement. This to provide voltage drop not created with replacement silicon vs. original selenium unit.

Great re: the photo anomaly of the EM35....We can rest easy now. :)


I will check out the B+ voltage and make a call based on that. I am guessing it would probably be a good idea to change it out to call it ready for full time duty. Thanks for the link. Any suggestions for packaging the caps and diodes in the old can?[quote]


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 Post subject:
PostPosted: Jan Mon 03, 2011 9:55 pm 
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Location: Malone, New York USA
Here is one:
http://www.radiomuseum.org/forumdata/up ... tifier.jpg

Snubber caps or no snubber caps......I'll leave that for others and keep my personal choice/ decision based on the informed comments, anecdotal observations and some minor study to myself.
IF you choose to try without snubbing, it is easy to solder the four diodes directly to the base. ( Common type 1N4007 diodes will easily meet the requirements)

I see this thread has wandered into the realm of the Electrical/ Mechanical Resto section.


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 Post subject:
PostPosted: Jan Tue 04, 2011 1:32 am 
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Location: Shiner ,Texas
The tall can is of course the main E-cap..it will be labeled with a 50uf..450 volt maybe 500 volt x 2 label...page 5 on the radiomuseum writeup has an excellent picture of the location of two replacement e-caps..below chassis..you can leave the bigboy above for show,disconnected.I have more than afew German radios with selenium rectifiers..none have gone bad..or showed any signs of doing so...yours will be that silver cased square of about 1 inch square by 1/4 inch high with a Siemens marking.I have replaced some of mine precaution.The original ones are still available...very,very hard to find.


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 Post subject:
PostPosted: Jan Tue 04, 2011 3:05 am 
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Location: Malone, New York USA
Sperrkreis wrote:
The tall can is of course the main E-cap..it will be labeled with a 50uf..450 volt maybe 500 volt x 2 label...page 5 on the radiomuseum writeup has an excellent picture of the location of two replacement e-caps..below chassis..you can leave the bigboy above for show,disconnected....yours will be that silver cased square of about 1 inch square by 1/4 inch high with a Siemens marking.I have replaced some of mine precaution.The original ones are still available...very,very hard to find.


Both the "E-cap" and the selenium bridge are in cylindrical housings and are originally located below the chassis deck for this model.
Siemens produced the flat-pack and AEG produced the black cylinders.
The 50/50 uf Elkos used in bridge rectifier configurations are typically 350 VDC working voltage and 385 VDC peak rating.

See this photo of 'before' some modifications to a 5088.
http://www.ppinyot.com/G/5088_b/IMG_2943.JPG


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 Post subject:
PostPosted: Jan Wed 05, 2011 1:58 am 
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Location: Shiner ,Texas
Dennis of course is right..I assumed too much...the S. Rec. to me in a German radio of this vintage/make is always a Siemens wafer type...Always be on guard for assumptions such as mine....sometimes radio buffs shoot quick from the hip.The make Philips ..during this era I believe was the only manufacturer who always used a tube... instead of a S.R.....Someone tell me I shot to quickly......


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