This is a wonderful sounding radio. The Grundig 5088 USA has all English wording on the radio. It has four bands, FM, BC, SW1 and SW2. The 5088 has five push button tone controls and four tone knobs.
Performance of this radio is surprising. I used a short antenna lead connected between the radio and the forced air supply duct work. The radio picks up many short wave international stations. There is an internal FM dipole and a "PU" input for a phonograph cartridge. A novel rotating ferrite stick antenna is mounted inside and rotated by the left outer knob for best BC station reception. Following are some restoration highlights.
Restoration was straight forward. All wax/paper capacitors were replaced with modern 630volt Premium quality PPT Metalized Polypropylene film dielectric, aluminum foil electrode, components. Several resistors were measured bad and replaced. All other resistors were extremely true to their tolerance. The selenium rectifier was under performing, not supplying sufficient B+. The rectifier was replaced with a diode bridge of 1N4007 and a series resistor to compensate the Vfwd (voltage drop) of the selenium array.
Alignment revealed the IF stages to be significantly off peak. The dial scale frequency alignments were very accurate and precise except for the lower SW band. Once the IF was properly aligned and the oscillators realigned all the bands and dial scales line up well. All alignments adjusted easily (once the German alignment methods/techniques were understood) and all sensitivities met or exceeded factory specifications.
This unit was in service in my 12 year old son's room at a "Torture Test". He fell in love with its detail and the functional EM34 tuning eye. (A "Dimmer" switch has been added to the EM34 to extend the phosphor life.) Listening to WWV (at 10 and 15 Mc) is soothing. I anticipate the rhythmic passing of the seconds and the slowly wavering signal strength will gently lull him my boy off to sleep (Here's hoping).
My son gave this radio a good work out. That way I am sure it will survive standard daily service. This is a beautiful unit that I restored not only to look and sound good but also to be a reliable "Daily Driver".
Some internal pictures during restoration.
SWII band oscillations:
After running the radio for some time (two weeks) it developed an oscillation problem on the SWII band from about 17.5 to 18.3 Mhz. Consulting with the experts at RadionMuseum.org found that component placement near the ECH81 tube. Particularly the capacitor C33 to chassis ground. One can put the radio near oscillation then with a plastic stick move the C33 closer to the tube socket to start oscillation. Moving it away prevented oscillation. The tube was weak on the triode section. That tube was replaced after the capacitor tweaking. The radio has not oscillated under "torture testing" (my 12 year old son) since then.
Tuning Eye saver:
I have added an STSP miniature switch "with quick disconnects" to the Tuning Eye B+ circuit. It is a simple bat handled switch that bolts through an existing vent hole. It has been soldered in between the B+ switch on the phono pickup switch contacts 4k and 4i and the tube socket. An original terminal strip can be found under the chassis for easy hook up. That is where the tuning eye socket lead wire feeds from above the chassis. All parts are available at Radio Shack. This modification is easily reversed.
Thanks to the participants at http://www.radiomuseum.org/ for all their help. An informative discussion about this radio can be viewed at http://www.radiomuseum.org/dsp_forum_post.cfm?thread_id=41660. Stop in and say Hi. There are extremely knowledgeable and helpful people at the .
Volume control repair
The volume control became intermittent. The radio would blast loud then go back to normal. Poking around the volume control found one of the wires to a solder lug when moved caused the failure. So repair or replace. I have no replacements so a delicate repair had to be undertaken.
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