I am trying to fix a GE SC-2307B 8 track player. 2 of the diodes on the board were destroyed by a failed capacitor that squirted hot capacitor juice on them (however, the board was lucky because the diodes shielded it from hot capacitor juice). All I think I need to do now is replace the capacitor and the 2 diodes. I found 2 diodes that are larger than the ones that were removed from the board that I might use as replacements, but they are quite a bit bigger than the charred remnants of the old diodes. Is it OK to use these as replacements?

We dont know anything about the diode part number, where it is in the circuit (so what it does), and where the capacitor is in the circuit (so what else it might have taken out when it was failing)

Besides, if the only thing that happened is an electrolyte splash on the diodes, then clean them ASAP with alcohol and maybe they'll be ok if it haven't corroded the leads into under the diode case

First ensure the diodes are sufficiently rated. Bigger not always mean higher load capability, it may depend on mounting style (often a copper plate on the PCB is used as a heatsink, bigger component may not fit close enough to be effective). The voltage rating should be at least twice of what these diodes are exposed to in the circuit (so a CT transformer rectifier it means 6x the transformer rms secondary voltage). The current is mainly given what heat the diodes are able to dissipate.
Then ensure the diodes are of sufficient commutation speed characteristics. You can not use asoft diode in a SMPS secondary circuit.

And you must make sure the diodes have sound mechanical support. So leaving the big diodes just "flapping in the breeze" just soldered to two tiny points is not any good idea at all. Soldered joints shouldnever carry any significant weight (a gram per joint of a small 1N4007 is good if the legsare short, but not anymore for a DO220 package soldered just on the ends of its legs). Dont forget any mechanical loading will cause the soldered joint to crack and fail. Often into an invisible "dry joint" trouble maker.

They are not that much bigger than standard 1n4007 diodes. They still solder to the board. They are right on the secondary of a transformer that outputs about 38 volts AC. I think the capacitor is right near the transformer's secondary as well.

They are not that much bigger than standard 1n4007 diodes. They still solder to the board. They are right on the secondary of a transformer that outputs about 38 volts AC. I think the capacitor is right near the transformer's secondary as well.

Then go for 1N5404.
The point was to not put there anything bigger then there already was.
And don't forget to clean the mess the capacitor has made, just recently I was fixing an induction cooker, where small capacitor had leaked and caused flashover over >1cm distance between power relay contact and coil pins. Board charred there, had to mill a big hole underneath the relay to separate the tracks.

i'd agree in5404 would be a good choice so long as the originals were not germainium or selinium? probably 1/1.5a silicon originals. look up the model of the unit hifiengine is good for schematics, just watch the lead size and fuse ratings for transformer though

i'd agree in5404 would be a good choice so long as the originals were not germainium or selinium? probably 1/1.5a silicon originals. look up the model of the unit hifiengine is good for schematics, just watch the lead size and fuse ratings for transformer though

No way these would be anything else but silicon. At the time before silicon, there was no hifi, maybe only vacuum tubes.
The silicon diodes (speaking about power rectification) replaced Ge diodes way sooner than the Ge ever become spread in any way.
The reason Ge power diodes never took off was the very high cost of Ge, their problematic behavior (prone tothermal runaway, so even ratzer low power component required sizeable heatsink to guarantee thermal stability) and not much advantage over Se or CuO based rectifiers used at tzat time.
It was the performance of the Si, which allowed the power diodes to be made at a reasonable cost, mainly the reverse leakage so the related thermal stability problem being practically nonexistent, so allowed small components to be used at reasonable power.

Plus Ge components were never using plastic packages, only glass (for the low power detection) or metal (for power components), again due to the thermal stability problem when any significant (mean 50mW or more) power was being involved.

No way these would be anything else but silicon. At the time before silicon, there was no hifi, maybe only vacuum tubes.
The silicon diodes (speaking about power rectification) replaced Ge diodes way sooner than the Ge ever become spread in any way.
The reason Ge power diodes never took off was the very high cost of Ge, their problematic behavior (prone tothermal runaway, so even ratzer low power component required sizeable heatsink to guarantee thermal stability) and not much advantage over Se or CuO based rectifiers used at tzat time.
It was the performance of the Si, which allowed the power diodes to be made at a reasonable cost, mainly the reverse leakage so the related thermal stability problem being practically nonexistent, so allowed small components to be used at reasonable power.

Plus Ge components were never using plastic packages, only glass (for the low power detection) or metal (for power components), again due to the thermal stability problem when any significant (mean 50mW or more) power was being involved.

There were a few germanium diodes in there but the 2 that were destroyed by the capacitor were silicon.

There were a few germanium diodes in there but the 2 that were destroyed by the capacitor were silicon.

Ge diodes were used mainly as a small signal diodes (e.g. detector rectifiers for VU meters, in the radio demodulators, various AGC circuits, electrically controlled gain stages,...), but not as power rectifiers.

As power rectifiers were used either Cuprox (for very low voltages, like 3V or so) or Selenium based rectifiers, then directly Si diodes.

Ge diodes were used mainly as a small signal diodes (e.g. detector rectifiers for VU meters, in the radio demodulators, various AGC circuits, electrically controlled gain stages,...), but not as power rectifiers.

As power rectifiers were used either Cuprox (for very low voltages, like 3V or so) or Selenium based rectifiers, then directly Si diodes.

I think these are power rectifiers.

I think these are power rectifiers.

Aren't they just silicon diodes in metal package? It was quite common for higher powercomponents.

Aren't they just silicon diodes in metal package? It was quite common for higher powercomponents.

No they have plastic packages.

Then they can not be Ge, Ge semiconductors were never packaged into plastic.

Then they can not be Ge, Ge semiconductors were never packaged into plastic.

I know the diodes are silicon, they are in plastic packages. The original ones were slightly longer but no thicker than 1n4007 diodes. Are 1n4007 diodes a good replacement?

I know the diodes are silicon, they are in plastic packages. The original ones were slightly longer but no thicker than 1n4007 diodes. Are 1n4007 diodes a good replacement?

The remarks about the Ge or not-power-rectifiers were about the other diodes you mentioned as "There are few Ge diodes,...", not about the main (blown out) rectifier.
The main rectifiers which this thread started about are clearly Si.

Because they were larger than the 1N4007, I would go for 1N5404..5406.
Or at least 1N4004 (the 4007 has about 50% higher voltage drop due to the diffusions in the higher voltage rated diode being of higher resistance, so even more than 50% higher losses; the 4007 has itmentioned in the datasheet, but the trend is real across the whole range), but these will be ontheir very limit on the inrush current surge charging the capacitor (sized for max load currents above about 0.3..0.5A).

Or incase there is a bridge rectifier topology and if the diodes are arranged in favorable way, you may use either KBP20x or GBPCx50xW (the "W" at the end is important, it means round wire terminals to be soldered into the PCB). These are bit heavier, but because have 4 point support, the solder joints are not stressed for bending.

The small round rectifiers are not that good for mainly the inrush current into the filter capacitors used for load currents above 300mA.