Tascam 52 help needed

[TimR]

Alignment,
using a MRL tape 250 nwb/m, I can adjust Repro Level Calibration with no problem at all, the high and low speed, of both Repro and Sync heads. Everything adjusts per manual with room to spare on the adjustments.
I'm having an issue with the Record EQ adjustment. The book says use a 400 hz, I only have 1Khz so I set with that, again no problem at all recording to a LPR35 tape that's pretty new. Now when adjusting EQ, I can record a 1Khz tone and meters read say around 0 on the VU meters, .3 Volts rms on the o-scope, when I raise the frquency to 21Khz, the levels drop off drastically to almost nothing on the VU's and the such a low level the scop won't read and when trying to adjust R318 (high speed) and R319 (low speed) I cannot bring the levels up but maybe a half a db if any. I can lower the freq to say 14K, levels dropping 7db on VU's
I have set the bias trap, run the procedures for the bias level for the LPR35 tape, I have not adjusted the BIAS tuning since I don't have a card extender anyways but testing pins 3 and 4, I get .305 ish rms on those pins so I think they are ok.
Since the sync head plays the calibration tape fine with no db loss, I'm wondering if my re-cap has negatively affected something. Both channels are the same, only the electrolytics were replaced using Elna Silmic II's except for the bipolars whcih were nichicons and the heads do have a slight fingernail groove but barely and look to be good, I know I need a better set of eyes on the heads but was wondering which way to go here.
So after all that blathering, what are your thoughts on this if you have a minute..
Also, putting back tension by hand doen't bring the levels up either.

 

[SkywaveTDR]

First the scope is used for phase comparisons not levels. The VU meter are adjusted to the external meter levels. I use Leader LMV181A or like dB or AC millivolt meters. You do not say what speed this is being done at. The 15 IPS decks I work on go out to 31.5KHz inside plus or minus 2dB at 0 Vu level. I had a Tascam 42 with SM900 tape go out to 50KHz in that variance at 0 Vu.
Your problems probably stem from your use of the over bias method of adjustment and the lack of proper test equipment. Once a Technician who is well seasoned shows you the way to adjust this machine in probably 40 minutes time the job will seem like a piece of cake.
Too many people get the idea that the record EQ is going to make up all the difference but the fact is they used the wrong over bias method of adjustment and they need to lower the bias to get the 1KHz sine and 10KHz sine to be about equal and that is on the external meter not the VU meters.. Adjustment of the bias also then requires a readjustment to the record levels- it is a back and forth process. Same on any machine and Otari MX5050 as well. I adjust 10KHz at +1dB relative to 1KHz level and then sweep if you have the ability to 28KHz at 15 IPS. Decks with 7.5 IPS are not going to give you the same 0 Vu response as the 15 IPS which is what the deck is built for- the second speed is always the compromise.
The higher flux density (250nWb/M) results in rolled off bandwidth at the lower speed. I think 7.5IPS can get out to 20KHz in some cases but sometimes maybe only 18 or 16KHz.
Sometimes you need to do the adjustments at -10 dB below the 0 reference due to saturation.
After doing many 52 and 42 and even 62 decks they are always a pleasure to work on and give the least problems of all Tascam decks. This is with 45 years of experience on these. I worked at Teac in 1982.
As Denny the Technician behind me at Teac at the time told me that real Recording Engineers do not use over bias as he was a Engineer at Streeterville Studios in Chicago but they adjust the bias for the wanted frequency response starting with 1KHz and 10KHz being about equal. Then small adjustments after that to get the other roll off frequency to the way they like it. Some things in a service manual are only meant for the assembly line and do not apply to repair Technicians location as we do the job more accurately and with greater detail than any assembly line would allow.