AKAI GX-365 Erase Head and record Head specs

[CDFixer]

I am working on an Akai GX-365D tape deck it does not record or erase. I have bias current at the heads, does anyone know what I should read for resistance of the head coils. One of the record head coils is shorted. The other reads 7.5 ohms. The erase head reads about 4 ohms across both coils and 2.2 across each.

I know the record head is defective (I have a replacement), not sure of the erase head I have replaced it with another that reads the same with the same results.

Transistors have been replaced in the record amps and they seem OK.

Any help would be appreciated.

Cheers Jim

 

[tapetech]

There is nothing wrong with your erase head. If the deck does not erase, then you have a defective bias OSC.

What is the P-P voltage on the erase head in record (measured on your scope)? And what is it's frequency?

 

[CDFixer]

Thanks for help, I found the problem with the erase bias which I knew was low. I had two oscillater boards and both were working the same. Your question led me back to the oscillater board and I found a crack in both boards both in the same place repairing the crack fixed the erase problem.

In 3 3/4 and 17/8. I now have at erase head.
Yellow wire 118 volts. 108 kHz
White. 68 volts
Red 108 volts
Black ground

7 1/2
Yellow 198 volts. 106.7 kHz
White. 98 volts
Red. Grd
Black. Grd



Now I just have the bad record head.

I have a complete head assy for this unit. Should I replace the entire assy or just the record head?

Have you ever seen a shorted record head? I disconnected the wires and it is a dead short.

 

[kaplang]

 

[Chip Chester]

Do you have a manual to know what the erase voltages should be at each connection? For example, it seems odd that Red is 108 at 3.75ips, but Gnd at 7.5ips. I'll admit that I've never measured voltage at an erase head on a consumer deck, but a voltage difference of 2X side-to-side would cause me to look it up.

 

[tapetech]

I have never seen a shorted erase head.

 

[Chip Chester]

When you're doing your measurements on the record head, have you disconnected all the wires from the head? Or are you measuring the coil in the head, plus the interconnecting wires, and the output circuitry of the record amp?

 

[CDFixer]

I disconnected the head. The head is shorted
Here is a picture of measurement of the bad side. The other reads 7.3 ohms. I had another head it reads 7.3 on each head.

This unit changes the erase head bias when in 7 1/2. The speed switch grounds the red wire at high speed.

 

[kaplang]

 

[CDFixer]

I have never seen a shorted erase head.

Neither have I, guess there's always a first time. Never under estimate the ability of a component to fail in anyway possible.

 

[tapetech]

A short is possible, but rare to encounter. The enamel on the coil inside could have failed (causing a short-circuit) for some reason. Corrosion perhaps?