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Go To 2500 USA chassis used to power up a 2602 USA chassis.

BLAUPUNKT Sultan

This six tube restoration comes from a Ham Fest. On inspection before dim bulb testing the chassis shows repair attempts. There are a few capacitors that have been replaced. The Diode bridge had been replaced with four silicon diodes in a plastic pill box. This will be replaced with a terminal board and dropping resistor or something more substantial. There is heavy corrosion of the fuse and just about all electrical contacts. The power switch shoes high resistance when closed and may need replaced if cleaning does not help. The power cord has been kindly cut off.

I clipped a cheater cord onto the transformer primary, plugged the cheater into a 100 watt dim bulb tester and applied power. The lamp stayed dim and the radio began to crackle to life. Once on direct line power the radio picked up stations on the AM broadcast and FM bands. Rather distorted but this is a great sign. No worries about IF transformers and the tubes are functional. The selector switch is in need of a complete cleaning as indicated by extreme crackling when the slightest tough or vibration occurs. There was no evidence of sound coming from the left or right tweeters. The EM80 tuning eye indicator is dark.

There looks to be a missing choke on the under side of the switch assembly. This will have to be investigated and replaced. The whole chassis need be compared to a chassis for any other modifications. It turns out these are two long wave band alignment capacitors. The fine wire coiled around the thick enameled copper stub needs to be wound or unwound to adjust the capacitance.

Further inspection shows many capacitors are original. There is a burnt original resistor in the audio section. Perhaps an output tube shorted or is shorted. This will be thoroughly investigated during restoration. Also an extended burn in period is to be run to shake out any bad parts (i.e., the corroded and rusted power transformer.

Restoration Photos

Electrostatic tweeter is dead.	Corroded contact.
Deteriorated foam dose not press the conductive film against the contact.	Donor foam rubber.	Make holes with a hot instrument.	Hot wire slice in two. The wire has been recovered from a cement high watt resistor.	Hotwire in series with a 100 watt bulb and variac.	Rust. Sanded and sprayed lightly with clear lacquer for insulation.
All apart.		Underside restored.		This needs patched. Most of the veneer was saved and glued back on.	Most of the veneer was separating from the base.
	This gasket turns into powered when touched.

The bezel receive the standard Clorox Clean up and Magnolia's Glayzit.	The tweeter speaker grills were subjected to the same cleaning.
		Good Night.

Silver Mica capacitor Disease The crashing thunderous roar in the AM band.

After hours of burn-in this radio developed static. It started as an occasional pop. Like the sound you get when some one turns an appliance on or off. It just progressively worsened. And the eye tube seemed to be fluctuating with the AM modulation. So I embarked on the delicate task of disassembling the IF cans, removing the internal mica wafers and adding external silver mica 600 volt caps. Join me below.

Take a photo of the wiring to the IF cans.	Get different angles.			After carefully marking what coil connected to which lug I unsoldered the fine wires.
	The base contains the wafer caps.	If the values are not marked on the schematic measure and mark the value on the base.	Yes with the low voltage of the meter it will read the mica wafer's capacitance rather accurately	Remove the rivit.
Wimpy wimpy	Grunt Arg (Tim Alen).	Now that rivet is gone.	pry it apart.	See the caps.
The blackened area is the trouble spot.			Snip off the contacts but leave a bit so the lugs do not fall out of the base.	Hot melt it back together.
	Mount your new caps. 1) 250pf and 1) 150 pf.	Installed.

Now for a quicker way to remove the mica wafers.

Take a wiring picture. Saves schematic tracing.	Move the lower slug out of the way. You will have to aligne the IF after all this work for accuracy.	See the caps?	Snip the long contacts leaving a bit so the lug stays in the base. Yes, the coil wires are still attached.	See how short.
	Uncut side. And Mark the cap values on both sides. You can not use a cap meter with both coil wires attached.	The schematic has the cap values marked.	Replace the cover	I use a clam since the hot melt gun is industrial grade heat!
Shoot some glue in the holes.	Move the slug back to where you think it came from. Not critical since you will be though and do a complete alignment.	Reinstalled.

The sensitivity all bands increased dramatically. I picked up several beacons on the long wave band below 350khz. The eye tube stopped bouncing to the music. FM was unaffected. There are not caps in the FM IFs.

It helps to use an earth ground with the LW reception. There are no RF bypass caps in this chassis. Besides to bypass (ground) LW may permit too much AC line current leakage.

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